That's know as CATA - cartridge ATA adapter. Project is described here: http://atari.8bitchip.info/astide.php
Second one. The goal was high speed, and it is achieved, with really special way of working, special SW.
Interest was low, and surely, one of the reasons was low compatibility - basically only for STE. May work on STs, but not guaranteed.
Now, I'm thinking about making some update. Keeping fast mode, and adding slower, more compatible mode, so it can work with ST, TT, Falcon too.
Users can select mode with switch on adapter. In case of low quantity producing it is still cheaper than going on 2 separated versions. Price should be little above UltraSatan price, and you getting driver, partitioner SW too, as it needs own drivers. Autoboot goes via cartridge ROM, btw. , so actually no need to install it. With improved TOS, it can work with 0 extra RAM usage (no need for extra buffers). Partitions up to 1 GB, 30 of them ...
2 connectors are possible: 40 pin IDE, or CF socket. First one seems as better - then can attach not only CF cards (via cheap, passive IDE-CF adapter), but classic hard disks and more interesting: IDE-SD adapters - that will be maybe most popular considering prices and low availability of CF cards.