NextBus was an east bay startup in the first dot com boom, actually, and my second job out of college. Muni was one of the launch installations. We were watching stuff like this (albeit with a decidedly clunkier hand-cooked map instead of Google integration) way back in 2000. I left in 2003, and they were acquired (without profit -- only investor shares were converted) a few years later.

Still, we didn't fail spectacularly, which says something. And going on 15 years later it's fun to see a bunch of my old code still running and doing useful things for society.

MTA has "bus time" which is not like nextbus in three important ways:

1: it is not a scam run by money grubbing jackasses to keep public data for private profit. 2: it is built entirely from open source software, and all the data is accessible with an open api.

3: the predictions are not a pack of lies.

http://bustime.mta.info/wiki/Developers/Index

Does a reasonable phone app utilize this yet?

No idea, it's a similar issue with the busses in LA, all of those that cooperate with the LA metro system are on nextbus, but the few that don't (santa monica) aren't on nextbus at all. I suspect it has something to do with cost of the hardware that the busses have.