Nevertheless, I'm afraid it will probably be abused quite a bit, until it becomes just another spammy thing ...
In my opinion, that's the key right there.
It's a bit like a Ponzi, or pyramid, scheme, I think, in the sense that it will work for early adopters, but will likely fall apart fairly quickly. The idea is pretty simple. Create a screensaver centered on your main keyword phrase and then let people download it from one of the many, many script directories (like hotscripts.com, et al). Programs to create custom screensaver executables have been around for at least five or six years, and every script directory will link to your site in their listing. Easy peasy.
The problem is that a screensaver executable is of rather limited use. I won't say they're a dime a dozen, but I sure wouldn't put the price much above a buck. The script directories are going to accept a few early adopters, but they're not going to allow their sites to become a landfill for screensavers of questionable value. Eventually, it'll be as difficult to get a screensaver into a script directory as it is to get a real estate site into DMOZ.
The idea, as Donna said, is a good one. But instead of trying to get away with limited value scripts, you should come up with a really good idea for a program in your vertical and then pay someone to write it for you. You'll be able to get all those links from the script directories legitimately. And, I would think, sleep a little better at night?