The app will be released on February 13, the day the HTC Inspire 4G launches in AT&T stores, but AT&T has not said which other smartphones will be able to host the new app.

When bundled with AT&T's 2GB Data Pro Plan ($25/month), the mobile hotspot app costs $20 per month and adds 2GB of extra data service. However, the 4GB allotment applies to all devices connected through the hotspot, and an overage charge of $10 per gigabyte applies if the user goes over 4GB.

For AT&T customers who are already paying $20 per month for a tethering plan, the new hotspot app-and the extra 2GB of data-will come at no additional charge, AT&T says. Phones carrying the hotspot app will connect with AT&T's HSPA+ data network, which has seen substantial speed gains over the past 18 months.