Unofficial Google Voice iPhone app GV Mobile+ is back on the App Store
GV Mobile+ can place calls from your Google Voice number, let you check your text messages and voicemail, set up forwarding to new phones, and even toggle call screening on and off. I had some issues with the GV Mobile+ marking some of my previously-viewed messages as unread, but the app works quite well for the most part.
If you've already bought the app on Cydia, and you want the App Store version for a non-jailbroken phone, you'll unfortunately have to shell out another $2.99. The developer did have a very brief giveaway to assuage his previous customers, but now GV Mobile+ is back to full price. Still, $3 is a reasonable cost if you use Google Voice on a daily basis.