I'm actually trying to do this too, I created a second acount on VoIPBuster and called from the PC to the account the DSi has, and I'm able to maintain a conversation very well, but the app can call back to your contacts, so someone needs to add that part and maybe add the option to write messages, so this can be the next BeUP with voice chat, and if someones crack the DSi then it will be just matter to cracking the cameras to have a video conference with your DSi, altough we would need to change the use of the VoIP for Skype, Yahoo or MSN messenger, wich is a U turn in the app itself...!!