Features?¤ Using Voice dial feature to make & receive phone calls.¤ Controlling the “Music Player”.¤ Compatible devices : Wired Headsets, Bluetooth Headsets, In-Car Bluetooth Handsfree , external speakers & few others.¤ Not a new technology & supported by most of the “mobile device” manufacturers.
Interesting facts!¤ Headsets when plugged in, all audio output/input is routed through them by the phone & handset speakers/ mic are usually* muted/disabled.¤ The audio output voltage typically lies between 1~2.5v on phones/mobile devices.¤ Almost all events on the phone are notified to the user with the help of corresponding tones/sounds.
Kung-Foo time!¤ What if, we added a microcontroller to the headset’s circuit to do malicious things?¤ Easily Possible stuff : ¤ Initiate phone calls without user interaction. ¤ Note duration of phone calls. ¤ Detect incoming/outgoing calls, sms & so on.¤ Not so Easy yet possible stuff: ¤ Record dialed numbers on the phone’s keypad. ¤ Enumerate all contact-names in the phonebook. ¤ Record phone calls. ¤ Can be remotely activated to carry out any of these tasks.
¤ Video of detecting numbers dialed on the phone’s keypad (Android based ZTE Blade) through just TRRS jack.
Things am currently working on (To-Do) :¤ Record calls, contacts, dialed numbers to a Micro-SD Card & play it back over voice calls.¤ Shrink the whole circuit to fit in your regular headset models.¤ Looking into advanced stuff using SIRI & the Android’s voice action/search features.