Hi Marc,

Yes, I see that for ShutterCount, but did you try www.EOScount.com? It is what I used for my 7D and 5DIII and on their website it says it will work with "any EOS DSLR that has Digic III or later."

Checking both the 1DIII and 1DsIII, both are dual digic 3 according to TDP specs page.

Hope it works for you,