I worked for a company that required me to tell them about all personal software developed for a period after I left the company. I suspect the intent was to make sure I did not create competing software... but the terms were clear and had a small reimbursement for filling it out and sending copies.

They got a bunch of custom ADND software for Windows CE. At some point, I got a phone call asking why I was sending them this stuff. It apparently irritated someone enough they released me from those terms.