Another third-party Google Voice app for Windows Phone 7 is here. GVoice for WP7 phones includes features like push notifications, send and receive free SMS, ring multiple phones, transcribe your voicemail, sync down your contact photos from your Google Contacts etc.
The GVoice app is available for $3.99. You can also download free trial having no push notifications.
Watch the video of GVoice in action :
GVoice in Windows Phone 7 Marketplace