Airvoice, if I understand correctly? So GSM handsets.
Something Nokia based would probably work well, something running Symbian... either an old S40/S60 device or an Asha 302 currently... maybe the Samsung GT-S3350, or Motorola EX226. I'm using a Nokia C3-00 (S40) myself, the wife is using a Nokia E61 (S60)... both can be had for around $50-75 on Ebay in pretty good condition and carrier unlocked.
If you want to look for specifics on features, try this search tool:
http://www.gsmarena.com/search.php3If you want a small recommended list of phones, I have some listed in
this article, or you can peruse a handful of new choices over at the
Shopping Hut (referral links - helps to support Technical Meshugana).
If you're wanting something Verizon CDMA based, it might just be easier to step up to Android when looking for a WiFi enabled handset.