Connecting a printer directly
to a smartphone or tablet can be a problem, in part because any given
printer manufacturer may not offer a printing app for any given phone or
tablet. Worse, even if there's an app for your printer, you probably
won't be able to connect the printer directly to your mobile device.
More likely, you'll have connect both to an access point and print that
way, or, as with HP ePrint Home & Biz app, print some files through the access point and others by going through a cloud-based print utility.
Wi-Fi Direct should change this very shortly. In principle any Wi-Fi
Direct printer should connect to any phone or tablet that offers Wi-Fi,
and any Wi-Fi Direct phone or tablet should connect to any Wi-Fi
printer. As partial proof, I had no trouble connecting to the Brother
MFC-8950DW with my Android phone to print photos using Brother's print
app. What's missing is an app that will let you print, say, Microsoft
Word files directly. As Wi-Fi direct becomes more widespread, however,
it's a good bet that connecting a printer to a smartphone or tablet will
become supremely easy. After that, apps will no doubt follow.