A friend of mine just uses her phone.

She has a cordless phone with a second handset and it has an intercom function. She just puts it on intercom and leaves one near bub and takes the other walkabout with her. Not sure about the range but I'm pretty sure it is further than a baby monitor. You can get long range phones too, but they might be a bit pricey!

Only thing to remember is to turn the ringer volume down on handset near bub, and if you do get a call, it turns the intercom off, so you'll have to go back to the house to re-set it.

Hope this helps.