Any question answered...

I'm surprised that Garmin and their ilk don't have a gear indicator (other than an one inferred from cadence / speed) - It might be useful for the anoraks when calculating power / intensity / effort at a particular gearing / cadence / speed.

£20 says that Garmin etc don't want to pay Shimano a licence fee, and might be a bit of an own goal if they align with one gruppo variety over another.

It might be interesting- I'd look at it on a graph for sure, but I reckon power/cadence/speed cover what you need to know.