Valve Shuns Phones, Handheld Consoles Valve does not intend to get mixed up in the handheld or phone market, the publisher was unequivocal in its answer: "no.

Valve Shuns Phones, Handheld Consoles

Valve does not intend to get mixed up in the handheld or phone market, the publisher was unequivocal in its answer: "no."
"We're about people sitting on their couches or at their desks," a company rep said. "We haven't forayed into that space. It's just not a space our engine has been looked at or optimized for."
Valve is currently focusing on some pretty big projects, with Defence of the Ancients 2 (DOTA 2) and Half Life 2: Episode 3 expected within the next 12 months.
The former might even be released before the end of the year, while the latter's fate is much less clear.