So bumping this thread as I also came across this kit for basically free at a DIY bike shop, and wanted to see if the sensors would be useful with an old Garmin GPS watch that I could make into a computer (they do!)

But, out of curiosity, I also had an old iPhone4 given to me which seemed like it would be a far more adaptable computer if I say wanted to add a power meter in the future, so tried to hook it up.

The problem seems to be that the iphone 4 is so old, none of the apps will work on it's OS. Is there any sort of workaround? My knowledge of Apple stuff is limited.