Having only recently marked its return to the handheld computing space with the iPAQ Glisten, HP seems intent on forging ahead with more hardware in the coming year. The above trademark applications -- filed in September and October 2009 -- mark out some very broad categories, but we can narrow them down a little with the help of some context. Given all the industry excitement over tablet devices, the Zeen could well be the name of a forthcoming slate-shaped machine and accompanying software, while Airlife seems to be planted firmly in the smartphone arena. The moniker suggests a software ecosystem rather than actual hardware, but that would make little sense with just one handset out there; if we were the betting type (and believe us, we aren't), we'd probably expect to see more mobiles coming from the computing giant in order to take advantage. Of course, companies don't always follow through on trademark applications, but it sure seems as if HP is casting a wary eye over the burgeoning handheld market (and / or planning to not get left behind in the months ahead).