An actual realtime update would prove problematic as you would need the app to automatically refresh every X seconds. This would a) Use a persons data and b) deplete mobile power. Ultimately who would want their restaurant app to be updating every 30 seconds. I wouldn't think that the realtime value is there for it. Waiting for a table, perhaps.
A better option would be to a) pull data as you load the screen, and/or b) provide a 'refresh' button.
As to whether the data changed, you can timestamp a last update (Eg: Restaurant 1234 last update)
Data as indicated previously needs to be handled remotely, or pulled remotely and held locally.
So, once you design your database, it would be...
1) 'List restaurants'
2) On restaurant selection> Load restaurant data
3) Present restaurant data
4) On refresh > Check last update > If newer Load Restaurant data. (Would save on data)
As an addendum, as the app regains focus, you can always go and reload the list/restaurant again to keep it current.
Some thoughts to play with.