Kik, a new chat application for smartphones that is quicker and more social than SMS, is showing impressive viral uptake. The company says it has registered 450,000 downloads in the first 10 days since going live.

And the uptake appears to be accelerating. It saw 150,000 new users in just 15 hours yesterday, chief executive Ted Livingston told me today, and the company is doing everything it can to manage the load.  “We’re just focusing on the servers,” he said this morning after temporarily freezing new downloads. See chart below for the growth pattern.

Kik has some notable technology under the hood; more on that in a sec.

First, here’s how the app works: Once you download the application (Kik supports the iPhone, Android and Blackberry/RIM), it checks your address book and recommends the friends and other contacts you are likely to know who already have downloaded Kik. You can then start chatting with them immediately. Like IM, it’s asynchronous, meaning it lets you see messages immediately, including when the person you’re chatting with is typing. Additionally, it lets you know when they’ve actually read their message.

I tried downloading it this morning, and it worked great. It was aggressive in pulling in all the contacts I “may” know. I didn’t recognize everyone it pulled. But this wasn’t really too bad, because they were only suggestions. The only people actually added to my address book in Kik were the people I messaged.

So how is it different from a service like say, Google Talk (Gtalk), Google’s IM service? After all, you can also opt in to GTalk for your mobile phone, even though you probably downloaded it originally to use on your desktop. Well, Livingston says there’s a subtle difference. You don’t know if your friend using Gtalk really is available immediately on their phone, or whether they’re using their desktop. They won’t necessarily respond, and if they don’t, you won’t know if they ever read the message. With Kik, you definitely know if they’ve read it — and you know as soon as they’ve read it. In this way Kik, is optimized for mobile use. “There’s a subtle difference,” says Livingston. “I think [the download rate] shows there’s a fundamental need for this.”

The service is like Blackberry Messenger, but cross-platform. Indeed, Livingston, 23, previously worked on strategy at RIM’s Blackberry Messenger unit, but left two years ago. He’s been building the product ever since. He tested an early version for eight months, which let him reach a total of 10,000 users. Those users were upgraded to the new version 10 days ago.

Here’s where things get interesting. If it can build its community, Kik has a lot of new territory to cover if it wants to. It can layer on functionality as it sees fit. For example, it can let you take pictures, and show friends what you’re seeing. It can then let you stream the music you’re listening to, directly from your phone over your friend’s phone. The same can be done for video. And it can be done over any device. While none of this is available right now with the app, Livingston demonstrated this advanced streaming technology to me, so it’s clear he can turn it on at pretty much any time.

During the demo of all this, we sat hundreds of miles away from each other, but he was able to remotely take over the Chrome browser (with my permission, of course) on my MacBook. He then played music over it — all while remotely operating this from his phone. All I did was enter a code that he gave me so that my browser knew to pair with the phone and allow the stream. (A QR code can be used, too.)

It’s pretty cool. Basically, Kik’s technology lets you wirelessly “sling” any content on your phone to any device running on any software.  This hasn’t been done before, as far as I know. Sure, AppleTV lets you stream iTunes content to the TV, but it’s a closed garden. You can’t run Apple content on other devices. Kik’s technology allows you to stream pretty much any content on any device with a browser, whether it’s a basic PC, or even a PS3, Wii or a Windows Media Center device.

It’s heady to think of the future of this application. I can scan my surroundings with the camera on my Droid, Blackberry or iPhone with merely a cellular connection, and then stream it to my friend’s phone. Or I can go to my friend’s home and stream an HD move from my phone onto his TV.

Here’s Kik’s magic: All of the data is actually stored on its servers, meaning that all of the heavy lifting is happening between the Kik server and my screen. So the content is not actually flowing from his device to mine. This reduces the latency that you seen with other products. It also means you don’t waste your phone’s battery life while doing the streaming.

Anyway, all of that new stuff is down the road. Kik will have to sort through music and licensing models so that it stays legal.

For now, Livingston is focused on the simple messenger application, which seems to be doing just fine.

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