UberMedia, the holding company that specializes in Twitter-based start-ups, has added its highest-profile company to date: TweetDeck, the biggest Twitter application not owned by Twitter itself.

UberMedia, run by Internet pioneer Bill Gross, will pay $30 million in cash and stock for the London-based company, which has raised less than $5 million from investors in the last two years.

The deal, first reported by TechCrunch, isn't done yet, but it's pretty far along, with signed term sheets, etc. All of TweetDeck's investors will take a portion of their payout in UberMedia equity, I'm told.

Both Gross and TweetDeck founder Iain Dodsworth have been trying to build businesses within the Twitter ecosystem, though it's never been clear how Twitter felt about that.

Gross, in particular, has had an uneasy relationship with Twitter: Last year, an earlier incarnation of his company tried to launch an "AdSense for Tweets" product at the same time that Twitter launched its own Google-like ad product, and that didn't go well.

The two companies have other things in common as well. TweetDeck has been shepherded along by Betaworks, the New York-based holding company/platform/incubator that also specializes in the Twittersphere. And Betaworks is also an investor in...UberMedia.

Here's an interview I conducted with Dodsworth in April, when the Twittersphere was particularly confused about the prospects of Twitter apps, like TweetDeck, that weren't owned by Twitter itself. Looks like this one turned out just fine.

Story Copyright (c) 2010 AllThingsD. All rights reserved.