I came across the term trap focus on the autofocus page of wikipedia, and it seems to be a very handy feature that triggers the shutter release when a subject moves into the focal plane. This feature seems to be built into only a small number of cameras though (possibly the ones with high FPS typically used for sports).
The wikipedia page also linked to an article called almost trap focus for cameras that don't support the feature natively. However, the steps described in the article seem to be more suited for macro or close-up photography, and that too using a FTM lens.
So, is there any way to trap focus on DSLRs without the feature, and without using specialized equipment?
As a reference point, I have the Canon EOS 550D with the 18-55mm kit lens.