The leader in digital delivery of the spoken word is taking its show on the road, literally, now that Audible (NASDAQ:ADBL) is introducing AudibleAir. The new service will allow Audible subscribers to download audio passages directly into their wireless smartphones. Until now, Audible would deliver its files through desktops and laptops. Subscribers on the move would then simply transfer the files over to their listening devices and stream on.

The service will be tested first through Palm's (NASDAQ:PALM) Treo smartphones. It's a sound choice, since the Treo -- combining mobile communication with PDA functionality -- has been Palm's major driver lately.

This is an important move for Audible. Even though just a small minority of its user base owns smartphones, the company needs to keep evolving to ward off any entrants that see spoken word as fertile ground for competition.

Companies like Apple Computer (NASDAQ:AAPL) and (NASDAQ:AMZN) seem like naturals to dive into Audible's niche, even though Apple and Audible currently have a mutually conducive relationship with one another.

Yet by erecting technological barriers, like AudibleAir, the company forces potential competitors to rethink their commitment to entering the arena. A rival to Netflix (NASDAQ:NFLX) wouldn't have to simply offer DVD rentals. It would have to outdo the regional distribution network that Netflix has in place. Likewise, a threat to FedEx (NYSE:FDX) wouldn't be able to simply deliver documents and packages. It would have to outsmart FedEx's efficient hub-and-spoke system.

That's why, even if the beta tests produce few interested subscribers, it's a path worth pursuing. It gives everyone else one more chapter to read in the Toppler's Manual.

Many were introduced to Audible in the October 2003 issue of Motley Fool Hidden Gems , when Tom Gardner placed the company on his Watch List as a promising $70 million company. Nice call: Audible is a $287 million company today.

FedEx, Amazon, Netflix, and Palm are all recommendations of the Motley Fool Stock Advisor newsletter service.

Longtime Fool contributor Rick Munarriz did not make a vocal recording of this article. He also owns shares in Netflix. The Fool has a disclosure policy. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.