A GPS sports tracker that keeps your training to itself
In January 2018, a researcher looking at Strava’s public global heatmap noticed something odd: bright, regular loops in the middle of deserts. Soldiers had been jogging around their bases with the app on, and the aggregated glow of their runs revealed the location, and sometimes the internal layout, of military sites that didn’t appear on any map.
The soldiers’ mistake is instructive precisely because they weren’t careless people; they were fit people using a fitness app as intended. Your runs tell the same story theirs did: they start and end at your front door, and they happen every Tuesday at six. A training log is a location diary with a stopwatch attached.
Sports apps are social networks first
That’s not an accident of implementation; it’s the business. The big training platforms are built around a feed: public profiles, kudos, segments, leaderboards, and the defaults that keep them lively. Privacy exists as a patch, hide the first 200 metres around home, and researchers keep showing how thin such patches are.
To be fair about it: if segments and a cheering community are what get you out the door, those platforms do that brilliantly, and nothing else does. But a lot of people just want to know how far, how fast, how high, without mailing their whereabouts to a feed. For them, the social layer isn’t a feature, it’s the price.
The recorder already in your pocket
Fenzly’s trip screen is a complete GPS activity recorder, no watch, no third-party account. Tap “Start a trip”, pick the mode, running, walking, cycling, or Auto and let the phone work it out, and go. While you’re out, the screen shows live speed, average, distance, elapsed time and heading, the altitude and climb so far, and your trace on the map, north-up or direction-up, recording on with the screen off. An optional auto-stop ends the session by itself once you stop moving; leave it off, and the session ends when you say so.
And because the phone can’t guess everything, the mode list includes what no sensor detects: bus, train, motorbike, boat, cable car, ski. The boat that a speed band once labelled a bicycle now has its own button.
When you stop, the session sheet opens: route, duration, average and top speed, the elevation profile with total climb. Rename it (“Lake loop”), file it in a trip category, Leisure, Sport, Professional, or one you create, and export it as a GPX file that opens in any mapping or training app.
Your season in numbers
The History tab turns sessions into totals: trips and kilometres by week, month or year, filterable by mode and category, your cycling kilometres this month, your runs this year, on the same private timeline as the rest of your life. Everything is kept by default; retention is your setting, and old traces are slimmed for storage only after their stats are frozen, so the numbers never change.
The group ride, without the grandstand
One genuinely social thing survives, at the scale we care about: your circles. On a group outing, circle members appear on your trip map, with a ruler along the edge placing each one ahead of or behind you and by how much. It’s a peloton, not an audience: sealed end-to-end like everything else, visible to your circles only. And for the “watch me finish” moment, a time-boxed live share does the job and switches itself off.
Where does it all go afterwards? Nowhere. Sessions live on your phone; a circle sees them only under the “Everything” sharing mode, in sober form, with full detail only for circles where you enable detailed trips. No server, ours included, learns your routes, your speeds, or that you run every Tuesday at six.
The honest limits
Fenzly is a tracker, not a coach. There are no training plans, no segments, no leaderboards, no community, and there won’t be: that absence is the product. If you want those, the GPX export is your bridge, including, yes, to a social platform, the difference being that it’s your choice, one outing at a time.
Two more, for the record. Elevation is estimated from GPS, so a barometric sports watch will beat it on climb accuracy. And a recording session keeps the GPS awake for real, this is the one scenario where the sleepy engine stays up on purpose, so a multi-hour outing costs battery like any tracker does.
Next in this chapter: the shortest, strangest proof of everything this blog has claimed. Ask us for your data, and see what comes back.