that's a good question!
My SD1100 (Ixus 80) does not have any thread.
My A570Is has a bayonnet. The same 52mm adaptor is sold on Ebay for A570, A590 A700 and A710 (see ebay item 250514435743), so all of them must have a bayonnet.
Actually, the WC-DC52 wide lens is listed on the Canon site as compatible with all the following models, so they should all have bayonnets:
PowerShot A10
PowerShot A20
PowerShot A40
PowerShot A510
PowerShot A520
PowerShot A540
PowerShot A570 IS
PowerShot A590 IS
PowerShot A60
PowerShot A70
PowerShot A75
PowerShot A80
PowerShot A85
PowerShot A95
(mostly old models, though, I don't think you have any !2MP here)
The LA-DC58G adaptor is listed as compatible with:
PowerShot A700
PowerShot A710 IS
PowerShot A720 IS
The LA-DC58C is listed as compatible with the PRO1 only
The LA-DC58K is listed as compatible with:
G10
G11
The A1000, A1100, A2000 do not list adaptors in their accessories and looking at the photos I see nothing like a bayonnet button or similar, so I guess they have nothing. That's odd. Can anyone that actually own one of them confirm?
EDIT: Anyway I would NOt suggest an SD-series camera for your project, they generally are too "automatic" and give you less conrol on settings (such as not being able to set a Tv Mode, for example, that I think you would be using on a camera mounted on a moving car)
My SD1100, for example, if there's a lot sun, instead of closing the Iris or shortening shutter time, turns on the ND filter and the shutter time goes up again, with the risk of blurring in moving situations. I guess you could play with the "Kids & Pet" mode, that probably tends to reduce the shutter time, but I guess you want more control.
