Bluetooth tape adapter
If you search for these. It seems they existed a couple years back. But you can't really find them nowadays.
There was a company that announced them at CES as well. But no product is actually available.
I'd started working on one just before CES, and have now been using it for about a month with no issues whatsoever.
Anyone can do it really, does require a small amount of soldering.
I used a Monster cassette adapter, and an HTC Stereoclip bluetooth receiver. I ordered a couple others, but they were to large to fit into the tape.
All in all, it lasts at least 6 hours on a charge. And it allows a wireless bluetooth input for any car that has a cassette, without any other aux input. Basically anything from the late 90's thru mid 00's.
The stereoclip is BT4.0, and has aptx. The sound is actually louder then the normal bluetooth input I've got in my car via the cd changer input.
If anyone is interested, I can post an actual writeup, and detailed pictures. Otherwise, for 50 dollars, you can add a bluetooth input in even the most unsuspecting of vehicles.