The newest version of Google Voice, when installed on a phone running Android 4.0 Ice Cream Sandwich, will put your Google Voice messages right next to your normal phone voice mail messages on the Ice Cream Sandwich native phone interface rather than having to go into the Google Voice app.
More after the break
This integration is similar to some of the deep Google Voice integration found on a number of Sprint Android handsets. Now you can respond to voice mail messages from Google Voice in the same interface they would come into if you got a voice mail message on your handsets regular number.
Your voicemails will appear alongside your outgoing, incoming, and missed calls in your phone’s call log and you can just simply touch them to play them. You can slow down the playback of the message which is great for when someone is telling you their callback number, or you even speed playback up, so you can quickly listen to longer messages.
You can upgrade to the latest version of Google Voice in the Google Play Store, keep in mind that this upgraded feature is only available on Android 4.0 Ice Cream Sandwich phones.