This weekend I helped Matt learn to solder and swap out the dead stereo in his van. While we were in there, we also equipped the older aftermarket unit with a bluetooth receiver. There aren't many good options for adding bluetooth to a car unit, most of them were either battery powered (some if you hooked them up to power would turn off and go into charge mode) and not really designed for a full time install. Logitech makes a a model designed for home stereo systems, but only comes with an AC plug for power, and requires a 5V power supply. 12V USB chargers put out 5V with enough amperage to power this, so I took apart one of the cheap chargers that I had laying around, desoldered the usb port and the cigarette lighter plug pins. I added a power pole connector for input power, drawing from some wires tapped into the stereo's wiring harness, and cut the stock plug off the AC adapter to solder right on to the board. The old case was taped back together to shield the whole works and everything powered up and tested great.
Back to the subject line, a little thinking about a project can create some handy shortcuts. Products designed for some applications can easily be adapted for others with a few minor tweaks and sometimes work better than others designed for your specific application.
