Unfortunately a gyro and accelerometer would only be able to provide the orientation of the device, not its location relative to the phone.
This would at least give you a compass heading that you could use when integrating the accelerometer data to give some kind of course over time.
It'd be pretty unreliable though and add a lot of cost.
I'd imagine you could get a rough location, but you'd need to go through some kind of calibration process first that involved going into different rooms/zones and telling the software where you were.
You might need extra reference sensors too. Ones that are in known locations that the system can use to scale the signal strength readings. That might help to combat some of the issues I mentioned above.
I'm not great at geometry but I figure it should be possible. Not sure about accuracy though.
The sensors in your phone won't help to work out where the sticker is. The bluetooth receiver in it is built to detect signals from any direction, so even if you rotate your phone, that doesn't help to work out which direction the signals are arriving from.
If you know the movement of the phone, you can determine which direction of movement causes the largest increase in signal strength change. So the app would be basically doing what you do to find something (let me move this way, oh I'm colder, I should go the other way) but at a higher spatial and temporal resolution.