I reckon a head torch is a useful thing to have as a nocturnal stoker, though I can't vouch for the off-road aspect. Probably doesn't need to be a full-on FRIKKIN LAZER as it's going to spend a fair chunk of the time illuminating the pilot's back. (Actually, that might be another genuinely useful application of the 'reactive' tech that Petzl are pushing - I find it's great for doing the washing-up when camping, occasionally handy for dirty fettling, and a liability[1] on a solo bike.)
[1] It's fine, you can turn it off.