Live streaming video company Ustream announced a new iPhone application today that will let you tap into whatever videos it is streaming live on the Web. Its coming-out party will be during the presidential inauguration next Tuesday.

Mobile video is a topic that’s gaining steam, along with the general excitement around mobile hardware and software advances. Ustream will be the first live video application on the iPhone as far as I can tell, although the still unavailable LiveStation app (broadcast feeds) was announced in last month.

This should get a big splash among the relatively small set of iPhone power users but mobile video will soon be standard issue for everyone else. It should also be a good promotional boost for Ustream, which has been streaming lots of live events, such as the TechCrunch50 and last week’s “Crunchie” awards.

The application isn’t yet available in iTunes but you can gain access to it by following directions on the Ustream blog.