Those using the Amber edition of Windows Phone on Nokia Lumia devices — probably a select few owners of the Lumia 925 at the moment — will notice an update to the “display+touch” application (setting) in their store. You can, if you have a compatible phone, access it via the link in the source below.
Glance Screen displays relevant information while the phone is locked (asleep). Previously, you could set the Nokia Glance Screen to be always on or “timed” for 15 minute, after which the screen would go completely off. Now, with this update, you can enable the “peek” option, which utilizes the proximity sensor, and turns Nokia Glance Screen on only when you “hover” (wave) your hand over the device. The screen turns on for 15 seconds to display Glance, after which it goes to sleep again. Note: it might impact your battery life, even if just a little.
Source: Windows Phone Store