Brad,
If you can, look hard at the Nextel Blackberry 7510, you have everthing the Nextel phone offers with the color Blackberry tacked in.
Also with the TCP/IP stack in the 7510, there are a number of third party apps that require the use of the Blackberry enterprise server on your network that isn't needed with the 7510.
For another project, we're getting a bunch with the Idokorro Mobile SSH so we're not lugging Thinkpads everywhere.
Something else to ponder is some Nextel plans have free incoming minutes.
Good Luck!