Yep - DisGirl is right. I got the Angelcare for this reason too - one pad in her cradle and one in her cot.

Also - the digital/analogue thing. I had to have the Angelcare digital because I have very bad mobile reception coverage in my area (God knows how given I'm 5kms from the CBD) - which apparently also means you have trouble with analogue monitors picking up other signals, or just not working.