Ahh for google voice you can use it through sip calling in the N9. GV is directly integrated into the contacts and the phone application.
http://everythingn9.com/how-to-set-u...-the-nokia-n9/

But the apps I would LOVE to be on the N9 is:
1. An app that you could copy text written on paper through the camera.
2. If its possible to make an application like bluestacks and Youwave for the computer which runs android application within the computer itself as a program, would it be possible to create an application like this for the N9/n900?