FatMaxxer VS SmartSpin2k

There's FatMaxxer app: https://github.com/IanPeake/FatMaxxer which does record HRV data and is able to export csv. Looks promising. Was able to record HRV with FatMaxxer and merge it to an simultaneously recorded activity (locus map).

Edit: maybe this was it? https://github.com/doudar/SmartSpin2k I don't know what your enjoyment for DIY stuff is, but this is doable.

This can automate resistance adjustment - https://github.com/doudar/SmartSpin2k

It’s a device that goes on the knob of a spin bike and turns it into a smart trainer. The project is in its 4th year and 3rd hardware revision. We went from no pcb to a pcb that was a carrier board for dev kits to now a full custom pcb. It works great! https://github.com/doudar/SmartSpin2k

Schwinn IC4 is a good bike. I hear good things about the Echelon Connect Sport as well. Both can be turned into a smart trainer with a bit of DIY effort using a SmartSpin2K to control the resistance dial automatically. It's a fun little addon that improves the experience. Worked brilliantly for me since I've got a very small condo with no space to bring a bike upstairs and onto a trainer. The spin bike was way easier to dedicate the space to 100% of the time and my partner also gets to enjoy it

Check out https://github.com/doudar/SmartSpin2k and add automatic resistance to your spin bike. Everything you need to build your own, or a limited number of pre built kits are available!

If the recumbent has a knob-based resistance control like a spin bike, you can use a SmartSpin2K device: https://github.com/doudar/SmartSpin2k with power meter pedals. (There's also a retail competitor, IDK about patents and such, but I always favor the maker version.)