The Circuit Sidekick iPhone and iPad App and the ElectroDroid Android App are highly recommended and have an impressive electronics toolset and resource libraries.
Decipher resistor and capacitor codes, calculate resistance needed for powering any LED, convert decimal, binary and hexadecimal numbers and more.
The iPad version of Circuit Sidekick comes recommended from principal design engineer and owner of PK Audiovisual, Paul Konikowski. His creds: CTS-D, B.S. Computer Engineering, Georgia Tech, LEED Green Associate.
Paul says, “Here are the top three AV technicians whom I think will benefit most from this app:
1. Bench Techs, who solder a lot, and want another excuse to have their iPad out on their bench.
2. Touring Techs, (a.k.a. Roadies, System Techs, Guitar Techs) who may not have done this in years.
3. Service Techs: no more second guessing your math when troubleshooting a problematic piece of gear.
For the Android users, check out ElectroDroid which has a collection of electronics tools including a resistor color code decoder with inverse look-up and an inductor color code decoder.
Check out the slide show for screen shots and more details of each.