Multiple wireless probes?

So I'm realizing I need to get more temperature probes and I was wondering something. If you have 2 or three dual probe set ups from the same manufacturer, won't they all be transmitting on the same frequency and thus not work to well?

I'm leaning towards using an Arduino board and setting it up to work on the 'net so I can watch it from my phone while at home and not have to worry about being near the back of the house for the receivers.