the kickrs don't do cadence or heart rate, but they transmit a speed. So you would need to put a cadence sensor on your bike if you want that. There is a mode where they use cadence to control the kickr, but you dont' have to use it and some people don't like it. As long as bluetooth is okay, you don't have to buy anything for your ipad. If you want to use your Garmin cadence sensor, there is a device that will translate ant+ to bluetooth. There were ant+ interfaces for older iPads, but there is a thread here that says they don't work on the new ones. The solution in that thread is one of these https://npe-inc.com/cableinfo/
Otherwise, if cadence and heartrate is important to you, you might want to consider getting wahoo bluetooth devices which also do ant+.