The Avengers Identicard is the handiest tool this side of a Swiss Army knife. Normally, it looks like a card with an Avenger's picture and signature on it, like a souped-up driver's license. But it does so much more.
First, the Identicard serves as a communications device. Each card has a flat-screen monitor to send and receive audio and video data. The Identicard can beep like a pager, communicate like a videophone, and record like a mini-recorder; it also has a virtually global range with satellite uplink. The Identicard can even be used as a tracking device to locate a missing Avenger via his or her card's unique signal.
In addition, it can act as a small computer with a numerical access pad. All by itself, this makes it an overpowered calculator. But with appropriate access codes, it can contact Avengers computers, which can then be operated with voice commands. The Identicard also acts as an ignition key for Avengers vehicles and as a key to Avengers bases.
The Avengers Identicards
are waterproof and can handle a lot of pressure, but they're not indestructible, so heroes should avoid using them indiscriminately to clean the exhaust ports on their boot jets. Bad things can happen.
In fact, handy little do-all gizmos like the Identicard can be notoriously unreliable at all the wrong times. They can be scrambled by sun spots, jammed by Ultron's electromagnetic leakage, invaded by nasty viruses, ionically polarized in their cross-fibrillated vibranium gromulators, well, you get the idea.