Thanks to Forum Member simonv, I now have a firmware for the VuTek DP92.
 
I have also found this website:
http://opentwin.org/blog/
OpenTwin.org has tools and instructions (French Language) for modding and hacking a very similar GSM/VoIP dual mode phone called the Neuf Twin Tact.  Just as the DP72 and S282 are related to the E28 R2821, the Twin Tact is a version of the E28 E2831.  All of these phones are very similar.
 
With the tools on the OpenTwin website, and the firmware file from the VuTek support page, it should be posssible to make a custom firmware for the R2821 type phones.
 
I'll post in this thread as I try these things, and I encourage others to do so as well.  With some luck, and this thread as notes, hopefully I'll make a Guides and Help page on the linuxslate.com website.
 
Here's a few starters (French) -- Warning the files provided for the E2831 may not work on the R2821/S282/DP72
 
How to extract the filesystem from the firmware:
http://opentwin.org/wiki/Firmware_maison
 
TT-loader, TT-loader tutorial page  -- Appearently Scriptable tool with ability to read, edit and flash the filesystem:
http://opentwin.org/wiki/TT-loader
http://opentwin.org/wiki/TT-loader/tutoriel
 
TT-tools -- Interrupts the boot process and appearently allows starting telentd or sshd.
http://opentwin.org/wiki/TT-tools