I did a similar build about a year ago, though with nicer Sunny bike that set me back about $600. I have the Wahoo he mentioned and it works perfectly. I also grabbed chest heart rate sensor so it actually displays in the Peloton app, but it really isn't necessary unless you're very focused on staying in zones. I'm at about 150 Peloton rides and couldn't be happier. It's slightly annoying to not be able to compete with the leaderboard (since the app doesn't know resistance), but generally I'm watching the recorded classes so I'm fine save ~$1500 plus the higher monthly Peloton fee. I'm interested to test out how Fitness+ compares!