I don't know how Micoach works, but if the device that records the workout has a GPS, then it can do much more, because the GPS can track your actual movement, not just count steps taken. So THAT would probably work with cycling. An iPhone has a GPS, so if you carried an iPhone with you for cycling, you can probably get it to do more than a nano.
For the heartrate, I think you need to get a separate Bluetooth heart monitor and link it to the nano's sensor. I don't know how it works, in terms of what it records and calculates, but the type of activity is probably an important factor.
I have 5th gen nano with the Nike+iPod kit, which I use for running.