Hi,

Just wanted to share this with you, I just tested it and it works on my BB 8820.

Talkonaut (http://www.talkonaut.com/howto_sip_accounts.shtml) can utilize a SIP provider (I am using BroadVoice) to initiate SIP calls.
In my case my BroadVoice allows me unlimited international calls (to certain countries) on my plan so getting it to work was highly desirable.

It does NOT use your wireless/wifi connection to transport the calls, but it uses data to initiate the call.

Here is how it works. If your SIP provider allows you concurrent outgoing calls (I just tested with BroadVoice and it worked) then you configure Talkonaut to connect to your SIP provider, now when you want to call a contact (say in the UK) you add them as a contact in Talkonaut (it does not interface with the BB contacts... annoying since you need to add the contacts one-at-a-time manually) and select "Call".
What happens next is that the Talkonaut client instruct your SIP provider to call both numbers (your cell and your destination number) and once both answer it connects the calls.
Obviously it only makes sense if you have unlimited/cheap (international) calling plan with your SIP provider. Then you don't pay (or pay less) for the international portion of the call (as it is routed through your SIP provider) while only paying for the mobile phone (incoming call) air-time/minutes.

I hope this helps. Let me know if you have questions about the configuration, I did not figure it out 100% myself but plan to learn more later.

Thanks,
Ix.

this is now IM plus works as well.

Thanks Carl, I will check IM+ too.
What I like about Talkonaut is that it is free, but well it is no really blackberry optimized (menus, contact integration etc.).

something else to check out is web messenger's skype client. it is not a true client in the sense that it talks over your BES server to a PC that runs your Skype software, but for the right situation it might work.