The T2i/T3i have the ability to record a low resolution video using only the center portion of the sensor, which is what the OP is referring to. Some HD purists call it "gimmicky" primarily because it only records in standard definition, not 1080 or 720, so they find it to be useless for their highbrow purposes.
bp is correct. The 5D does have the 5x and 10x "zoom to focus" feature. But you can't record this. I understood the OP to be asking about recording, not punching in for focus.
Just to clarify: The 550D/T2i does not record the zoomed/cropped video at HD resolution. However, the 600D/T3i DOES. The T3i has a digital zoom feature that essentially uses a cropped part of the sensor, effectively zooming in. This is recorded at "full resolution." Indeed, the 3x zoom is actually a bit higher resolution than the T3i not zoomed in (both record at 1920x1080 but their actual resolutions are in the neighborhood of 1600x900). Because the sensor is not downscaling, the zoom feature also eliminates moire - a very nice feature to have sometimes.