You're right. There's been a lot of vapourware but never anything that anyone independent of the manufacturers could get their hands on. I've met several people who said they were going to do it, and several who actually tried. Neither group succeeded. This is basically a folk-myth for wishful thinkers, along with the million-year light-bulb and the car that runs on water, where 'the patents' were bought up by a non-existent cartel who felt threatened by such things. Such views betray a certain ignorance of how patents work.
Cheers,
R.