I have been trying to use voip over wifi on all voip apps and found only one does it and its vonage. I am rooted so I don't know if it will work on stock roms . The app is available from there website and it says it will work on 1.5 I don't know if you can receive calls yet, but I wasn't looking to receive calls because I get all my VM on google voice and it comes threw wifi if I don't have service then I can call them back on my vonage wifi service. I spent alot of time today trying Truphone,Skype,and other apps that worked on my N95, but Vonage works great on my Hero.You have to put a couple bucks on your international calling plan to activate but then when you call local it does not charge you so it looks like it will work indefinitely as long as you don't use up the money you put on it. I am on villian 5.3 and loving it.