In windows phone 7.8 (not in previous versions) you have the ability to start and stop video recordings by tapping the screen. Before, you were required to use the hardware camera button for video recording.
im sure that the Bluetooth is inactive when the screens locked, unless you have a device connected. this saves battery. I have tested this theory by leaving Wifi Bluetooth 3G on all day and the battery hasn't been adversely affected.
also a great way to get extra battery is to turn off the mobile data and wifi, phone cant update and so the battery just keeps on going. coupled with light usage I managed 3 days (only turning off at night ).
I tried the "ease of access" setting that you mentioned on my NOKIA LUMIA 710,
but when i try clicking on the "Speech for Phone Accessibility",
it doesnt budge :(
what do i do?
I love the Voice features on the L710 btw :)
Do reply soon!