As GP has said, you can log into Sprint WebCapTel, then "Wait for Call" and input your telephone number to wait for a call. Someone calls you at the telephone number GP posted (the 800 #) then follows instructions, they can reach you, absolutely. I've done it a few times -- it's neat!
As for EVDO networks, nope -- at least not today. Maybe in the future. I've been able to use my Sprint HTC Mogul on WiFi and running the new Opera 9.5 beta browser to do it.
