For those who don't know about the radar function: It notifies you (using a push notification) that you are close to a certain location which you might want to check into.
So I want to know if Windows Phone lets you monitor your current location in the background on a regular basis.
Windows phone allows background processes to run in the background, and be aware of positional information. Prior to Windows Phone 8, these are limited to a cached location that the operating system updates every 15 minutes or so. These same background processes could react to this locational information and react in a similar way.
With Windows Phone 8, app developers can gain accurate, and up to the second positional information whilst running in the background, so this could also do the same, with a higher level of accuracy (as well as allowing more flexibility for things like tracking a mountain bike route, etc.)
On the Windows Phone Dev Center, you can find a how-to on how you would go about implementing this in your app, in case you are a WP dev.
http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj662935(v=vs.105).aspx
It describes two steps:
I expect the 8.1 update for Windows Phone to incorporate more changes in the area of geofencing.
