T-shirts would seem to be among the most low-tech of products.

But the art of T-shirt production, especially shirts with out-there designs and slogans, has become a decidedly Web-savvy affair. With online T-shirt companies sprouting like hipster facial hair, the simple T-shirt is being transformed from a cheap scrap of cloth into an object of obsession by a mix of techies, graphic designers and do-it-yourself scenesters.

Consider a startup called Reactee, a company that’s bringing together two trends – text messaging and the online T-shirt craze. Just to understand what Reactee is doing requires an intimate acquaintance with habits unfamiliar to many people over 35.

Here’s how it works: You choose a slogan or phrase (“TONY IS ALIVE”), as well as an accompanying keyword (“TONYLIVES,” let’s say), and Reactee will print a T-shirt with your phrase, keyword and just enough information for people to contact you when they see your shirt. By texting your keyword to a special Reactee text messaging number (41411) that’s printed on the shirt, a response you’ve written – in this case, your “Soprano’s” theory – is sent via text message to the person who entered your keyword.

I don’t doubt a significant percentage of the people reading this will be thinking something like, “What in the world are you talking about?”

If this sounds strange to you, then you probably don’t exchange text messages with your buddies between latte breaks. (Reactee’s online demo will help demystify the process.) But if you’re a 22-year-old who lives on his phone, you will get the idea immediately – or so Reactee hopes, as the T-shirts don’t come with detailed instructions.

They just say something like: “STOP AIDS,” and then “TEXT NOAIDS TO41411 TO HELP.”

Presumably the person intrigued by your T-shirt could just walk up to you and start chatting, but maybe that’s just too 1978 for texters.

Yes, I’m dating myself, but I’m not exactly a T-shirt neophyte. In fact, I have bought several T-shirts from Threadless, a company that’s made a name for itself by selling T-shirts with designs created by users and submitted online. You visit the site, you vote on shirts, and Threadless prints the best of them. When you a buy a shirt from Threadless, you feel like you’re not just buying a piece of clothing, but a conversation piece that’s also a limited edition art work, albeit one that’s likely to fray and fade over time.

Publishers have even gotten into the act. Indie press Popular Ink sells limited-edition T-shirts with limited-edition books. The logic behind this is explained as follows: “Everyone needs a shirt and everyone needs a story.”

The online T-shirt culture is a decidedly participatory one. If you have a T-shirt design of your own, you can have it printed, and offer it for sale, by uploading the artwork to spots like CafePress, GoodStorm, Printfection, Spreadshirt and Zazzle.

Other spots sell T-shirts within a specific genre – Jinx for gamers and geeks, PalmerCash for the retro look, and on and on. Preshrunk (preshrunk.info), a T-shirt Web log, covers the scene with mini-reviews of shirts.

Just beware of getting addicted. I am. In the course of writing this, I bought one T-shirt (from Defunker), and I have my eye on a few others.