You can check the consistency of the kernel "file" and compare a MD5 / SHA-1 of known good kernel. Assumption here that the kernel is loaded into healthy hardware. Depends on the spirit of the question. I do agree, running kernel looking at itself... chicken::egg.
Ask the users! I'd answer a poll at the bottom of your page... Where is your page?
Answers:
1. Way way too many (I'm to the stage of browsing that I'm posting comments! ehhe).
2. Great answer to the initial question so I'm pretty happy now.
3. Very very far from angry (see 2)
4. MacBook Pro (10.5.5) 2.4Ghz Core2 Duo 4GB RAM.