My Fly 12 gets swapped between 2 bikes, it would be nice to have the ability to store the 2 sets of tramline measurements instead of having to change them.  

Second suggestion, how about a built in level?  It would need to be on the side so it would work whether the Fly 12 was right side up or upside down.  But it would make transferring between 2 bikes (or just checking mid ride) much easier.