Here is what I'm considering survival apps on my Android phone (in addition to several reference apps mentioned above, in no particular order) :
[list]
[*]Alpha Bravo encoder - encodes a phrase to Alpha-Bravo and Morse code (can vibrate it in Morse code).
[*]Cardiograph - measure your pulse (using camera and LED light).
[*]Cookbook - engeneering solutions cookbook.
[*]Several LED and Screen light apps, one of them can encode Morse code to series of flashes.
[*]Shake flashlight - turns your screen white on vigorous shaking (great when you can not look at your phone to touch icons).
[*]Cooking - eBook app.
[*]Earthquake Alert! - online resources aggregator.
[*]ElectroDroid, Electronics Tool Box - apps aiding with electronics devices improvisation.
[*]EMF Detector - basic metal finder app.
[*]GPS Essentials - various GPS tools collection.
[*]Military Mountaineering - eBook app.
[*]Night Vision - camera booster app.
[*]Offline dictionaries - various languages dictionaries to download.
[*]Physics Cheater - another reference app aiding in improvising with very well categorized everyday physics formulas.
[*]Scanner Radio - online only app for monitoring of public police and fire radio channels.
[*]Scrolling Text - great tool for sending your message up to 100 feet away or even farther (e.g. from your car to another car running at 80 mph both). No wireless connection required
[*]SkySafari - astronomy app which can be used as navigation aid (using stars, planets, moon, and sun).
[*]Smart Compass - compass over the video overlay. Good over the map and over the real view.
[*]Smart Tools - a set of various useful tools like rulers, protractors, distance meters, level, metal detector, sound and vibration monitors.
[*]TwoTouch Timer - really quick set timer app.
[*]Sound grenade - produces very loud and annoying sound, seems even piercing walls.
I have several dedicated GPS mapping apps as well. Using Evernote to collect and organize everyday data as it's coming in. Using SPB Wallet to store sensitive information (e.g. passwords, lock combinations, credit cards, e.t.c.).
(Hmm, List tag seems to be broken on the forum)