Tapulous is readying 3 applications that they will release in the AppStore. 2 of them are old friends reworked just a little bit. Twinkle (the geolocation based twitter client) and Tap Tap Revenge. A new application not released to the public yes is called Friend BOOK.
» App Store – Tapulous releasing (tap tap revenge, twinkle and friend book)

Twitxr is a native Twitxr client.

The service Twitxr is quite like Twitter but this service focuses more to Picture sharing than just sending quick updates of what you’re doing like Twitter.
The official statement on there website is:
» Twitxr 0.5-3