That's a battery grip for the 40D, now on the 10D this I found was a wonderful addition to the camera adding comfort and ease of use. This was something I instantly missed with the 40D, but unlike before I've decided to take a risk and order a generic Chinese copy of the Canon BG-E2N grip. Now I've no great expectations of this being in the same league as the genuine part - how could it be Canon part = £150+ vs. Chinese part = £25 (delivered) but on the other hand it is just a plastic box to hold some batteries/switches /wires! Anyway, with the Sigma lense needing a repair(?) I don't really want to invest too much money in accessories - sooner put the money toward a better lense.
Born in 1956 (so getting on a bit now) I'm married and have two wonderful children we all live in Devon in the South West of England - on the Cornish border.