Have you tried out qgvdial and it's phone integration component qgv-tp?
Also, if you're looking for a way to dial out directly with the equivalent of the gmail dial method, then please do a forum search for threads by xur17. One of them talks about making this work on the n900 with a fair degree of success.

The links for qgvdial are in my signature - I hope this interface doesn't hide them. If it doesn't, search my handle.

Edit: For the signature.