Have a lawyer (in IP/contract/employment law) look at the document and your situation before you quit your job. It'll probably only take him a few minutes to review it. A couple hundred bucks and you'll know for sure.

I had this exact same situation recently. My day job was in mechanical engineering and I had a website that I did on my own time/computer. My lawyer said that since there was no connection between my day job and my website that I was fine. The agreement I signed was very similar to yours in that it had catch-all phrase like that, but my lawyer didn't seem concerned.

I also emailed my boss and legal counsel at the day job to review my website and I asked if they thought there were any overlaps or conflicts of interest. Both said no, so I have documentation they they disclaimed rights to my website, just in case something ever came up.

YMMV though. Just call a lawyer and get it over with.