We use GA & Omniture. The business love using GA Realtime analytics.
Literally if there are 400 more people on the site than normal, they like to know.
It would be awesome to have a check type that called GA Realtime API and fetched this data. Within WPM you could set min/max values (if you so wished) to see this data.
There are two ways to do this as I think:
1) Do this specific integration - it isn't so huge?
2) Do some much larger piece for being able to set up a check which is extensible. To be able to 'build' a custom check out of whatever logic you want.