FHSS is what you want (Score 1)

You'll find out on the market 2.4GHz phones that fall into 2 catagories.
DSS - Digital Spread Spectrum
FHSS - Frequency Hopping Spread Spectrum

The DSS ones will interfere with your 802.11b wireless connections.

The FHSS one will not interfere. FHSS changes the exact frequency that is uses, hops around, many times a second. So it's not on the exact frequency as your wireless base station long enough to cause any problems.

Panasonic does a good job on 2.4Ghz cordless phones and makes a number of models a that use FHSS technology.

My guess is that other company's that are saying they are 2.4Ghz-Friendly are using FHSS.

I've used Panasonic FHSS phones successfully with both 802.11 b and g wireless.