Right, org-timer-item is what it's called. I keep forgetting about this, but it would've been useful for me today.
If you start a list with:
- 0:00:00 :: Something
(Or any kind of h:mm:ss numbers) when you use org-insert-item, it'll start a timer and insert elapsed time every time afterwards:
- 0:00:00 :: Something
- 0:00:00 :: Timer actually starts
- 0:00:05 :: 5 seconds later
- 0:00:15 :: 10 more seconds