A few months back I installed a few apps straight from the internet. One was an ability to run Ruby scripts on my phone, the other was Grooveshark. Both times, an Jellybean 4.2 flagged up a warning saying these programs have the potential to access my camera and microphone, but I ignored them.
Now I'm getting a bit paranoid. With the macbok pro, when the camera is accessed, a little green LED lights up. It's 'hard-wired', as even security programs (for when your macbook's stolen) can't take a photo without the LED lighting up. Luckily, the LED is brighter than your average laptop-theif, and it only lights up for a second, so no problem there.
But with an android you literally have no clue. I tested out the security program Cerberus, and it took videos of audio samples using my Galaxy without the phone giving a hint what was happening.
I've deleted Grooveshark (it's an abysmal app anyway), but I'm still worried about some other program from months ago recording me.