Controlling arduino with a bluetooth remote

Hello,

This seems like such a simple and common thing to want to do but I've been all over the net and there doesn't seem to be a (simple) solution available. I have a very cheap 2 button BT remote shutter dongle which I'd like to be able to use to trigger the arduino. From the research I've done this doesn't seem to be possible using the ubiquitous HC-05 BT module as this doesn't support HID class devices. So my thought process on all this is:

  1. Is there any way at all to accomplish this with an "out of the box" HC-05?
  2. If not what is the simpliest procedure for flashing the HC-05 to support HID? All the ones I've come across online seem very involved.
  3. Is this for sure possible with the RN-42? i.e. using the BlueSMiRF Silver for example? The vast majority of tutorials online involve creating a HID device with the RN-42 rather than using it to allow devices to connecting to the arduino.
  4. Barring doing this properly via HID, is there any method of detecting raw BT radio signals? Even this would be enough to do what I want. Trigger an action just on the event of receiving any kind of single in the right frequency band.
  5. If this is just not doable with BT, what are the cheapest options using an RF dongle rather than BT?