Dumb Ideas Done Dirt Cheap: a privacy-focused linux handheld device like PinePhone or Librem 5 would be a great candidate for an OSM powered bike computer application.
tie-ins with the ANT and bluetooth stuff is probably the hard part, but for commuters and tourists it would be really nice to have something private and purpose-built.
no instagram selfies here
The cool thing about doing this is on linux is that Qt convergent QML development is a no-brainer. it'd be a fun project if I felt like it, then use NixOS to bake images purpose built for bike-computer usage and a desktop app;
a small daemon which spits out dbus messages that the qml app can consume and other frontends?
you can buy a small "suunto" USB module which can do ANT+ controlled
Track your heartrate on raspberry pi with ANT+ a python-ant library
WAITING support for bluetooth LE and those devices?
WAITING support for ANT devices?
WAITING open street map tiles and bike routing
we got bike-route tiles and we can be smart about POIs to show