Well i know Vincenzo had a Nokia 6310i during the 1st part of the development,I assume thats the best phone but a little old now.
The main rule is that your phone must have AT command support,if you can contact your phone via hyperterminal your good to go.
The Problem is different AT command set's are supported by each manufacturerbut you can use ATSniffer to help identify the commands your specific phone supports (if at all) and customize which ones are used by RRM.
For those of you who have WM5 phones,you still need to purchase Phoco!
I understand there is an app called PhocoAdaptor which you can run on your phone to interpret GSM commands.You can then use that app to recieve commands from RRM or FF.