I think your "free typing test" might be sort of a marketing vehicle if you could provide embeddable badges of results for blogs, or shortened links to your results for a Twitter stream, FB, etc...
Or maybe not. The sort of people showing off their mad typing skills probably wouldn't also be people who want to buy your service :)
My intended market was the kind of person who googles "learn to type", finds Mavis Beacon, and then orders a CDROM from Amazon. That's what I did a couple of years ago, and it was a painful experience.
First I bought a downloadable version, which then sent me on a wild goose chase for Stuffit Expander, which was required to uncompress the image. Then when I finally got that, it wouldn't run on my OSX Mac.
Finally I learned that there was in fact an up-to-date version available for Mac, but only on CDROM. So then I purchased THAT (yeah, I paid twice!) Ultimately, the software was great, but getting it installed was a major PITA.
I imagine that there are a lot of traditional desktop apps like this that you can only get on CD (or dodgy software downloads). That's the "niche" I'd like to target.
Or maybe not. The sort of people showing off their mad typing skills probably wouldn't also be people who want to buy your service :)