01
Precision GPS
5-second sampling with Kalman filter smoothing. Foreground service keeps tracking reliable when the screen is off.
Privacy-first · Local-first · No account
Track every
mile.
Share what matters.
A quiet activity tracker for runners, cyclists, and hikers. Precision GPS, route replay, Apple Watch companion — all on your device. No social feed. No leaderboards. No analytics SDKs.
5s
GPS sample
0
Trackers
watchOS 9+
Watch ready
USA-default · respects your locale in the app
9:41
Morning run
Burlington loop
LIVE
DISTANCE
3.37mi
PACE
7'50/mi
TIME
26:24
Heart 152 bpm↑ 276 ft⌘ 312 cal
By the numbers
5.0
GPS sample rate
seconds — Kalman-filtered
0
Trackers
no analytics SDKs
<2%
Battery / mile
adaptive sampling
~12 KB
Per activity stored
on-device, encrypted
Record
Start fast, track precisely — on your phone, your watch, or both.
Features
Everything you need.
Nothing you don't.
02
Splits & elevation
Per-mile or per-kilometer splits, elevation profile, gradient zones, calories — all computed on-device.
03
Heart rate zones
Pulled from the watch via HealthKit. Time-in-zone breakdown after every workout — no cloud round-trip.
04
Route replay
Watch your activity unfold on the map as a time-lapse. Export as a video clip for stories — or keep it for yourself.
05
Watch companion
Native SwiftUI watchOS app with complications, live workout summaries, and standalone tracking.
06
Battery-aware
Adaptive sampling drops to 10s on long activities. A 4-hour ride won't drain your phone.
Live Activity
Your run, on the lock screen.
Pacelit drives a native iOS Live Activity. The lock-screen card and Dynamic Island both update every second — pace, distance, and elapsed time stay glanceable without unlocking your phone.
- Identity row — activity glyph, label, and live status chip
- Hero row — distance · timer · rotating Apple-Fitness-style stat
- Action pills — pause / resume and lap from the lock screen
- Dynamic Island — compact glyph + timer in the bubble
08:147'26/mi
RunLive
Distance
1.12mi
Timer
08:14
Pace
7'26/mi
Pacelit · now
Heart-rate Zone 4 reached — 158 bpm
Apple Watch + iPhone
Two devices.
One workout.
Native SwiftUI on the watch. React Native on the phone. They talk over WCSession — phone GPS as source of truth, watch streams heart rate. Track standalone on either, sync when reunited.
9:41
Pace · /mi
7'50
HR
152
Distance
3.37
WCSession
Bidirectional sync. Background transfers when both apps wake.
9:41 · Live Activity
Pacelit · Run26:24
3.37mi
Pace
7'50
HR
152
TrackHistoryProfile
Understand
Replay every route and see what the miles are telling you.
Route mapping
See your route. Replay it. Share it.
Apple Maps on iOS. Google Maps on Android. Routes render live, with polylined trails, mile markers, and gradient zones.
Sunday long run
Jul 14 · 6:42 AM
Distance
10.42mi
StartFinish↑ 466 ft↓ 453 ft
Moving time
1:24:54
Auto-paused at lights
Elevation gain
466 ft
Hill segment +28 sec
Avg pace
8'14"/mi
GAP: 7'40"/mi
Elevation profile
10.42 mi
Built for movement
Three sports. One quiet tracker.
Each activity gets its own dialed-in summary — the metrics that matter for the way you move, nothing you didn't ask for.
City laps to long trails
Run
Per-mile splits, cadence, vertical gain, GAP-aware pace.
Road, gravel, commute
Ride
Rolling distance, average speed, max speed, climb categories.
Trail, peaks, backcountry
Hike
Elevation profile, gradient zones, time at altitude.
Training load
See if you're building, peaking, or overcooking it.
Each bar stacks the seconds you spent in each heart-rate zone. The number on top is the day's training load. The same chart you get in the app — tap a bar to inspect.
Hover or tap a bar to see the per-zone breakdown.
Week load
432
sum of daily TL
Z2 share
35%
aerobic base time
ACWR
1.08
Sweet spot 0.8–1.3
Heart-rate zones
Z1 · Recovery
Z2 · Aerobic
Z3 · Threshold
Z4 · VO₂
Z5 · Anaerobic
Sample data — your own zones are derived from a 30-day resting-HR window using the Karvonen formula. ACWR = acute (7d) / chronic (28d) ratio.
Workout summary
The full story of your run.
Computed on-device.
Splits, heart rate zones, calories, gradient time. All of it calculated from your raw GPS + HealthKit data — never sent off your phone.
- Per-mile split with pace delta
- 5-zone heart rate breakdown
- Calories from HealthKit BMR
- Gradient-adjusted pace (GAP)
Sunday long run · 10.42 mi
A new personal best on the Burlington loop
1:25:42
Time
8'14"
Avg Pace
1,142
Calories
Splits · per mi
Best mi · 7:42
1
2
3
4
5
6
7
8
9
10
Heart rate zones
Avg 152 bpm
Z1Z2Z3Z4Z5
Trust
Private by architecture, not by policy — here's exactly what Pacelit doesn't do.
Local-first by design
Your activities never
leave your phone.
Mainstream fitness apps are surveillance products with route maps attached. Pacelit is the opposite — a working tracker, no growth loop, nothing to optimize against you.
On-device storage
Activities live in an encrypted SQLite database on your phone. Routes never touch a server.
No backend
There isn't a Pacelit server you sign in to. Nothing to subpoena, nothing to leak.
No analytics
No Mixpanel, no Amplitude, no Segment, no Sentry telemetry. Crash reports are local-only by default.
No account
No sign-up flow. No email. No social graph. Open the app and start tracking.
Compared
Pacelit vs. typical fitness apps.
Same core tracking. Different defaults around your data and your attention.
Capability
Pacelit
Typical
Account required
Cloud sync of routes
Third-party analytics SDKs
Social feed / leaderboards
Start/end points visible on shared activities
Subscription tier required for full features
GPS, splits, elevation, HR zones
Apple Watch standalone tracking
Story-card export
Bulk GPX export of full history, no paywall
Open-source core (planned)
Activities stay on-device by default
"Typical" reflects the default settings of the most popular social fitness apps as of 2026. Pacelit doesn't name them or run comparison ads against them — that would require analytics we don't run.
FAQ
Common questions.
Does Pacelit need an account?
No. There's no sign-up flow. Open the app, grant location and motion permissions, and start tracking. Activities live on your device only.
0Where is my data stored?
In an encrypted SQLite database on your phone. Coordinates are stored as binary blobs for compactness. Preferences live in MMKV. Nothing leaves the device unless you explicitly export.
1Does Pacelit work without a phone?
On Apple Watch, yes. The native watchOS app can track standalone — pace, distance, heart rate. When you reconnect to your phone, it syncs the workout over WCSession. Phone GPS becomes the source of truth when both are tracking.
2How accurate is the GPS tracking?
Pacelit samples GPS every 5 seconds (10 seconds in battery-saver mode), then runs a Kalman filter to smooth jitter. A foreground service keeps tracking reliable when the screen is off — no missed miles when you pocket the phone.
3Can I export my activities?
Yes. GPX export for any single activity. Bulk export of your full history as a zipped archive of GPX files. No cloud lock-in — your data is always portable.
4Will there be a paid tier?
The core tracker stays free forever. A future Pacelit Plus tier may add training plans and advanced analytics, but everything in the core feature set — GPS, route mapping, splits, watch companion, share cards — stays free with no subscription.
5What about Android?
Android is in active beta. Same React Native codebase, with Google Maps replacing Apple Maps and Wear OS support planned for after the iOS 1.0 launch.
6Why no leaderboards or social feed?
Because they trade your attention for engagement metrics. Pacelit is built to help you record and review your activity, not to maximize daily active users.
7Get the app
Lace up.
Hit start.
Free to download. No accounts, no subscriptions for the core tracker. iOS first, Android in beta.
Launching soon · v1.0.0iOS 16+ · watchOS 9+Android 8+