I am currently working on a new project at home to integrate an Arduino microcontroller into my exercise bike. The bike more or less broke several months back. The problem was that the circuit for increasing or decreasing the resistance on the bike wheel died. This meant that while I was pushing the buttons, nothing was happening and I was stuck on the last resistance set.
I was able to troubleshoot this and hook a 9v battery directly to to the motor that drove the resistance. Reversing direction worked perfectly and I was able to control it. Problem is that it was a bit of a pain riding it to get off of it and adjust the bike.
I originally planned to simply hook a battery to it and replace the switches. I thought then it might be really neat to integrate the microcontroller into it and build one of those expensive bike computers out of it. I'm going to see if I can access the hall effect sensor on the bike otherwise I will attach a magnet and my own sensor. I should be able to get mileage, etc from there. The current computer only has a few features. I was thinking the improvement would be that I could add a course into the microcontroller allowing me to increase difficulty and have more fun.
More news to come as the project progresses.