Magic Mouse etc.
I have had similar trouble with Magic trackpad and mouse and occasionally magic keyboard. They seem to loose connection usually on wake-up. I tried everything then at last I explored the Bluetooth preferences (In system preferences) I looked at "Advance" tab and changed the "Bluetooth-PDA-Sync" from "modem" to "RS-232". I have had no trouble since. I don't understand why this setting should apply to these items but I hope it is a permanent cure.