I think it would technically work if you use the "push" notificaiton option. This shouldn't need anything extra from the RADIUS client (aka the AP) and the RADIUS server only needs to send an ACCEPT/REJECT.
However I can see several caveats.
- Roaming could be a real pig. Especially if you are between two APs in a fringe area. You may get a lot of push notifications if re-authentication happens.
- Every time you walk into coverage (such as when you come to work every morning) you'll get a push notification.
I think it will be a real pain.