1. Out Of Milk
A shopping list app, with all the regular features, but the cool thing about Out Of Milk is you can share lists, with your partner or your housemate. This means that if one of you runs in to buy say, Cornflakes and skimmed milk, then those items are taken off the joint list. You can also add additional details (like a preferred brand etc), and the pantry section shows you all the items you already have.
2. Word Lens
Need to translate a sign in a foreign language? Word Lens can help with that. Just hold up your phone's camera and it will do the rest.
(Bear in mind you have to buy language packs within the app. Currently: English/Russian, English/Portuguese, English/German, English/Italian, English/French, English/Spanish.)
3. Strides
Strides helps you to build a habit, or reach a goal, and looks very pretty while doing so.
Get it on iTunes. If you want something with fewer bells and whistles, Achieve It! runs in a similar vein. And if you're on Android, then GoalTracker will do the job.
9. 7 Minute Workout
This app, developed based on a workout routine published in ACSM'S Health & Fitness Journal offers exercise options for even the most time-poor.
11. Citymapper
This app means that you'll never be late again. Calculate the most efficient route, or the most cost-effective, or a rain-proof journey. Available for: London, Paris, Berlin, Madrid, Barcelona, Milan, Rome. New York City, San Francisco, Chicago, Washington DC and Boston.
12. Select Who
No more wasting time making decisions. Who gets the last piece of bacon? Who chooses the film to watch? Let this app streamline your choices.
Get it on Android.
13. Clue
16. Account Tracker
Keep tabs on your finances, and track your spending.
Get it on iTunes. For Android, Money.co.uk reccomends My Money.
17. Delectable
This app helps you level up on your wine choices. Scan a bottle to find out more, get expert opinions, note and rate the wines you like. Very efficient.
Get it for Apple devices. For a similar app on Android, try Vinvino Wine Scanner.
Bonus: BOINC
Make your *phone* more efficient. You can help to study diseases, predict global warming, or discover pulsars, by allowing the Berkley Infrastructure for Open Network Computing to run jobs using the unused computing power of your device. Basically this means that within parameters (like, when plugged in, on wifi, with a good battery life), your phone can collect, compute and transfer data for any number of scientific projects within the scheme. Cool!
Available on Android. For a similar thing on Apple, try Genes in Space a game which analyses genetic data for cancer research.