Monument Valley is a gorgeous game, and fun to play with its Escher style landscape puzzles, but it's very short (only 10 levels so far). If you can find it on sale I'd highly recommend it. You can probably blow through it in a few hours.
Most mobile productivity apps leave a lot to be desired when compared to their full computer-based counterparts.
I use Concur to submit expense claims as the organization uses it (Concur is owned by SAP) but i have to say that I use the mobile version far more than I use the computer version. Especially for approving travel authorities and claims, the mobile version kills the computer version.
Was at a public health (population health) seminar the other night on new media etc in popn health. As an aside one of the panel's orgs had tested around 50 apps that calculate BAC, out of about 200 known ones, and none were accurate. None were the same answers even. One even claimed to breathalyser by breathing into the phone mic. Not a joke one.
Seminar was great. Any decent research shows its mostly hype and marketing and evidence is not just weak about effectiveness of Facebook, Twitter, apps, even forums, it's worsen than weak.
But great potential in African underdeveloped countries for use of non networked non smart old mobiles.
Random factoid: Australia has 108 mobiles for every 100 people!