Geotagging Toggle UX 180x300 Is this Twitters secret iPhone app?One of the notable things about the way Twitter has run its business up to now is that it has never got into the app business. New screenshots suggest that might be changing.

Twitter has always left development of everything except the core Twitter website and API up to third parties. It even bought the service’s search technology in from a third party.

Now developer Jesse Stay, the man behind Social Too, has spotted what looks like an iPhone app used internally by Twitter.

With the new geolocation feature being tested internally and the new version of Seesmic Desktop featuring the ability to read location from tweets that use it, how is Twitter generating location tags for its test tweets? From the looks of the screenshots Stay has uncovered, by using a secret iPhone app.

Now, we’re not suggesting that Twitter is about annoy its third party developer community by launching its own iPhone app. Given its bare-bones look this is probably noting more than a test app for adding geolocation data to tweets.

Still, it’s fascinating to have a look ‘behind the curtain’ at the development process behind one of the decade’s biggest web success stories.

Larger screenshot below:

Geotagging Toggle UX Is this Twitters secret iPhone app?