mobile equivelent for suspend & resume

[andrew at midwestcoastmedia.com]

I have a mobile app that I'm looking to implement "Enable Background  
Execution" in now that the plist hack is no longer required. Is there  
a simple way to track how long the app has been in the background?  
Basically, I'd like to initialize the full stack if the user has been  
gone for a certain amount of time to make sure everything is up-to-date.

I found "suspend" and "suspendStack" (with their "resume" and  
"resumeStack" counterparts) but they aren't supported in mobile. They  
do exactly what I'm trying to do in the dev desktop environment but do  
nothing on mobile.

My app already writes some other data to a small preference file on  
the device when the user does a variety of activities, like moving to  
a previous card with the backKey on Android, so I do have a timestamp  
for recent activity. I just don't know how to automatically check when  
a user returns to determine how long they've been gone.

--Andrew Bell