If Apple’s iMessage service looks threatening to SMS, what about a service that makes texting free to anyone with a U.S. phone number – with or without a device?

Pinger today is debuting Pinger Textfree Web, offering a way for anyone with a Web browser to text for free. With Pinger’s Textfree Web, users choose their own local U.S. phone number and can communicate for free via text message to any U.S. mobile phone, as well as to more than 18 countries. The company is also throwing unlimited, free picture messaging into the mix.

Pinger says it’s the only company that provides users with a personalized U.S. number from which they can send and receive texts. It can be done from any computer, and existing Pinger Textfree users on iPhone, iPod touch, iPad and Android devices also can log into their account via the Web to send messages.

“We built Pinger Textfree Web based on feedback from customers who wanted to text from the convenience of their computer,” says Joe Sipher, co-founder and chief product and marketing officer for Pinger, in a press release. “Now anyone can text even if their phone is lost, out of battery, or if they don’t even have a phone.”

It’s not completely taking SMS out of the game, however. In an interview, Sipher explains that the communication between devices uses the IP or data channel, but from Pinger’s servers, the messages use the traditional SMS networking. In fact, Pinger is among the top 10 carriers in terms of volume when it comes to SMS.

Right now, the great majority – like 80 percent – of Pinger users are on iPod touches, so it’s actually adding more SMS users who otherwise wouldn’t be using text messaging, he says. The core user base is 12- to 17-year-olds, and a lot of them don’t have a text messaging plan, but they’re sending texts to their parents who do.

Pinger started out as a shop for providing asynchronous voice service but changed course and started focusing more on text messaging, although it still offers a voice service too. The company needs local phone numbers in the countries where it wants to expand, and it’s in the process of securing those but those processes vary by country.

Last week, Pinger announced that users of its Textfree for Android app reached parity with iPhone users in just five months. The company also launched its Pinger Textfree for Android 1.2 with Facebook Chat integration.