You can use the Pin Change Interrupt feature to wake up your Arduino from sleep. You will get 2 interrupts, one when motion is detected, and the other when the sensor times out.
I would have thought that any transmission medium (wired or wireless) with hardware that is capable of generating a signal to indicate the reception of a piece of information would be able to do this.
Yes, you can power the sensors whilst the Arduino is asleep. You will need to keep the PIR sensor powered in order to receive motion detection interrupts.
As an aside, as you are using sleep to extend battery life, then you need to look at your various sensors and decide if they have to be powered during sleep. Do they need to be awake whilst your Arduino is asleep? Any sensor that needs to wake the 328P would obviously need to be powered.