You're best to get someone from SMSGupshup to contact us. It all depends on exactly what you/they want to do. I have had conversations with them in the past, and they know about FrontlineSMS, and were interested in working with us at some stage.
In our project we used the Wavecom GSM Modem and we used a Nokia phone for Frontline Forms. I don't remember exactly which phone it was, but if you go to http://www.frontlinesms.com/forms/index.php you can see a list at the bottom of phones that will work.
Please let me know if you have any other questions. Good luck.