It's really quite easy to use just about any old wireless, portable phone 
with a Model 100 or 200 for truly* portable computing.
    Using RS's acoustic coupler cups, simply attach the mouthpiece cup over the
microphone and the earphone over the earphone, using some hefty rubber bands.  
Even though the cups don't even remotely match the contours of most portable 
phones, this technique still works very well.
    Apparently the signals thrown out and detected by the 100/200s are strong 
enough to overcome strange sorts of line noise in normal circumstances, and 
this makes for a good margin for error in receiving conditions with wireless 
phones.  I've found that, even when the portable phone is in a marginal 
receiving area where normal conversation would be rough, still the modem tones 
come through strong and data is clean.
     Wireless phones can be had for as little as $50 (less in some areas and 
when on sale).  Try it out and see how you like it!
                   -- Thom Hartmann