Ask HN: USB cable, laptop, phone, how can I take a photo?

I normally wouldn't post this here, as HN isn't a support forum. However, my Google-fu has failed me utterly. Either that, or the information just isn't out there.

Or it's impossible.

I have a laptop, a USB cable, and a phone, and I want to get the laptop to cause the phone to take a photo. How can the laptop, via the USB cable, trigger the phone to take a photo?

Added in edit: I have two phones I'd like to do this with, one is Android, the other is a Blackberry.

Thanks in advance,