Google has recently updated the Google Voice app for Android, and as someone who used this app on a daily basis — I can say that this update is the most welcomed yet. As for what was updated, the app now has a new feature called Inbox Synchronization. This means that (should you want to), you can have the app notify you of a new text message or voicemail “within seconds.” The reason for the excitement here is that in the past the lowest time interval was 15 minutes. And when dealing with SMS messages 15 minutes can be a long time for someone waiting for a quick reply. For those using the Google Voice app on Android, you will need to visit the Market and update. But then after that is complete you can adjust your settings and receive the near-instant notifications by launching the Google Voice app and then going to the Menu -> Settings -> Refresh and notification. Once there make sure the box for Synchronize Inbox is checked.
Read [Google Voice Blog]