RIM’s rumored TV app will need shows. Fast.

Word on the street is Research In Motion is looking to bring some TV magic to its line of BlackBerry smartphones. According to NewTeeVee, multiple sources have hinted at RIM announcing a new TV download service at the upcoming CTIA conference.

Again, this info is considered unconfirmed (a RIM spokesperson said the company doesn’t comment on unannounced apps), but here’s the skinny so far: The RIM subscription service would allow users to download full-length television episodes to their BlackBerry devices via WiFi. Once an episode is finished downloading, users would be able to watch the locally stored copy on the device. Sources also say the subscription fee would could cover unlimited downloads, and that multiple broadcast and cable networks are already on board.

Ah, but here’s the nagging question: Which shows would be available? I’ll circle back to that in moment.

If this rumor has legs, then RIM’s success lies in the trifecta of decent video quality, reasonable mobility, and engaging content for the service. In terms of video quality, a download-based service should be able to offer quality superceding streaming mobile TV services like MobiTV and SlingPlayer Mobile. On the mobility front, RIM’s purported reliance on WiFi connectivity is a mixed bag — but no worse than the iPhone’s current subsistence on computer access for downloading shows from iTunes.

But, let’s be honest — with quality and mobility likely addressed, the only thing RIM has left to fumble is its catalog of shows.

Though BlackBerries can already access online video hubs like YouTube, a premium subscription service is a different creature entirely. To keep viewers glued to their BlackBerry screens, RIM must work with the networks to ensure it offers a robust catalog of in-demand content.

To be fair, it’s unlikely that RIM can replicate the success of iTunes this late in the game (especially with the latter’s dense catalog of shows and movies available for purchase). However, a consistently updated, prime time-centric catalog of shows could provide users with a reason to regularly visit the service. A similar formula has worked well for the ad-supported Hulu, and it’s likely that RIM would have to offer a similar (if not better) catalog to justify its monthly subscription fee.

Regardless of RIM’s mobile TV aspirations (whatever they may be), the company’s heart is definitely in the right place. Analysts are already predicting that video will drive 64 percent of all mobile traffic by 2013, and RIM has already nabbed an impressive 19.5 percent of the market as of last year. If these trends continue, then a TV download service from RIM could see a windfall as consumers grow increasingly use to the notion of watching full-length content on the mobile platform.

That is, if there’s anything worth watching.