Palringo is going to be the closest thing you will get for PTT on the Sprint TP2. Its kinda simple and its free the only problem is, is that the other person has to have it on their phone as well.
Mobile
Palringo is purpose-built for mobile phones.
We’ve designed Palringo to be easy to use on the move, allowing you to easily type chat messages or send photo and voice messages when you’re out and about.
Plus with our special design we make sure staying connected to your buddies on IM isn’t going to cost the earth. Palringo is free to download, there are no subscription fees, no hidden charges and no monthly subscriptions. The exact cost of use depends on your data package - but just 1MB of data lets you send 100,000 words of text, 32 picture messages or up to 15 minutes of voice messages.
Palringo works on just about every phone under two years old so you don't need to buy an expensive new handset. Some of the mobile devices we support include:
Plus with Palringo no-one feels left out, because it works everywhere in the world.
http://www.palringo.com/en/us/
and for non U.S. you can change the language at the bottom of the page.