i'm rather amused and confused by your asking....i don;t think there is any software in the world that could satisfy your asking unless you master the art of ninja which have been rumoured for centuries that they possed a wonderful art of being invisible...that supposingly i believe could allow you to take photos of others secretly in great comfort.
all you need to do i think is to put your hp in silent mode (some hp can be very loud when u snap a photo)...turn off the flash if there is one (you don;t want your target to get a rude shock of your paparazzi type flash light) , slid open the camera cover if there is one...pretend that you are smsing...make a quick but natural aim at your drooling target and snap a photo...what happen next would depend on your luck, or fengshui if some believe.
sorry but that's all i could think of.
