Cheers for the reply, and a fair point on the second idea. Admittedly, there is that big flaw where the visitor can nip off and make a cup of tea whilst viewing my page, which would limit its mainstream usefulness.
I'll explain a bit about my site in particular. I'm using WordPress to create an online games arcade site, where each post features a different game. As an added incentive to signed up members (and it might make interesting reading from the admin perspective), I was hoping to let them view a page so they can see how long they've spent playing individual games.
That one's not a hugely important request personally, so if it doesn't exist already then I can probably make do without it. But I think the first suggestion is something that can be useful to others, and somewhat surprised that Google didn't bring back any plugins.