Would this work as a wireless solution?
I am a bit dreaming of someone implement a DOS driver, for my PC-XT, do the SD/CF adapter need a driver i do not think so?
So it would just be a matter of driver for EYE-FI part of memory?
Have anyone tried EYE-FI on newer computer, can it connect to a router?
Are you just trying to get wifi on your XT or just trying to get files to and from the SD card? The first wouldn't be possible because the eyefi would be on a IDE bus, which is not a universal bus, its meant only for disk access. The second, while might be possible, wouldn't be easy, it would require fully rewriting the eyefi firmware, as its built its only programmed to SEND files to another computer (and only JPG, MPG, and RAW files at that), not receive any.
To the first, trying to get an XT (or other old PC) on WIFI, just get a simple WIFI>ethernet bridge and plug it into a plain wired ethernet card in the XT.
To the second, just put a CF or SD slot up front on the old PC so its easy to reach, then pull the card and sneaker-net it back and forth with your modern PC, not wireless, but easy enough.
EDIT: Not trying to poo-poo on the idea of #2, I think it would be cool, and I would probably end up buying several more eyefi's if it was possible to use it bi-directionally for any file transfers, but its a project that is well beyond my abilities (someone would have to likely know assembly for whatever CPU the eyefis use internally, which if its a custom job is probably not published).
As far as using a eyefi in a CF adapter, it WILL work, however GREATLY reduces the range on it, many people do use them in higher end DSLRs in CF adapters (some have gone as far as removing the metal casing off the SD/CF adapters to help with wireless range).