I would like to transfer my Vonage number to a VOIP provider who will provide SIP credentials to use with my N900. Mobile phone service is bad at my home, so SIP over WiFi would provide much better service. Simultaneous ring and voicemail are import features I would like to keep.

So far http://www.broadvoice.com/ is the leading contender.

I like http://www.phonepower.com but it appears that they do not release SIP credentials even though they allow you to bring your own hardware.

Can anyone suggest a SIP provider they are happy with?