The most audacious start-up pitches are those that propose changing people's communications habits. No matter how clever a company's technology or gorgeous an app's interface, getting users to adopt new modalities of communication is perhaps the hardest job in tech.

It's a social challenge as much as a technological one, which means that if you get it right, your technology spreads from person to person--virally, as the overused term calls it. Lately, social start-ups have been adopting strange, mutated viral models: Path is a social app that launched with a bizarrely limited way to join networks. Color opens you up to pop-up social networks based on physical proximity. Both clever but far outside most users' comfort zones.

CloudTalk has a clean and fast interface for asynchronous voice messaging.

A new app, CloudTalk (previously Pana.ma) is a person-to-person voice and video messaging app. On paper it looks like an unpleasant mashup of voice and SMS, but it's not. CloudTalk is a very smart system for sending asynchronous voice (or video or text) messages to your contacts, and I believe its interaction model is appropriate for the way people communication today--especially kids.

As CloudTalk founder David Hayden (formerly of Magellan and Critical Path) says, as we discuss the younger generation's growing reliance on text messaging, "It's not that kids don't like to talk. It that they don't like phone calls." CloudTalk is designed around recording voice messages. You can also send photos, videos, or text, but the interface favors voice. Conversations appear in a list window much like a iPhone's display of an SMS thread or an instant message chat.

I was skeptical that this app would add anything worthwhile to the standard quiver of smartphone communication tools we all have, but to my surprise it works well, and it's worth using. I've never seen an application that does such short work of sending voice messages or that makes it so straightforward to mix modalities in a message thread. If you want to reply to a voice message with text or video, it's easy. Or vice versa. The only thing you can't do yet is call or FaceTime a person for a real-time discussion from within an asynchronous thread.

It's easy to add people to your CloudTalk address book by scanning through your smartphone's address book to find people who are also CloudTalk users. You can also search the online directory for users you know, much as you can with Skype.

Press to record. The big red button says this is a voice app, although you can also send text messages, and record photos and videos.

CloudTalk can also turn a one-to-one thread into a multiparty conversation. You can, additionally, join BBS-like discussion groups. (See also: Beluga, owned by Facebook.) But the star of this show is person-to-person communication.

When you're using it, CloudTalk does not feel like a sparkling new idea. It seems rather obvious. That makes it fast to learn and easy to use. But while it's different enough to be valuable, it's not such a conceptual innovation that it will scare potential users away.

The app is available for iPhone and Android, and it shines on smartphones. There's a second-rate Flash-based Web version as well.

The business Hayden tells me that the company is making its platform available to other developers' for example, see the dating app AtZip, which uses CloudTalk technology. Other business, like news organizations, might set up their own apps for citizen reporters or set up their own private groups, with exclusive features, for which CloudTalk could charge a fee. Hayden says the company can make money from providing these services. There may also be a freemium model, in which paying users get things like transcription services. If the service gets the number of users it deserves, a freemium subscription might generate revenues.

As much as I like this product, I'm less optimistic about this company being able to make good money in day-to-day operations. I wouldn't bet against a nice acquisition by a communications or social company, though, like Skype or Facebook.