It will depend on the distance you will have between the monitor and the receiver. We have been through 3 different monitors trying to find one that doesn't make that awful buzzing interference noise.

We tried the Angelcare monitor and a Childcare monitor with no success.

Our house is 2 storey and we also have wireless internet and our cordless phone was causing interference because it was on the same frequency. One of those two, can't remember which one, used to buzz louder when the microwave was going. We turned off the wireless internet and the phone and although it cut down the amount of interference, the 2 units were just too far apart (and obviously didn't have line of sight).

We then tried the Tomy monitor (it was a Winnie the Pooh Sleepy Friends one, bit tacky, but it was recommended by Choice magazine at the time) and the Tomy was the hands down winner, blessedly silent. And DS was very taken with the Winnie the Pooh nightlight in the end so I got over it!

(We gave the other monitors as gifts to friends having babies).