Check out the awesome RipCurl video Timeslice Films created using 52 Canon EOS Rebel T2i cameras. Very cool!
Can you buy T2i's by the case?
Nathan, who has worked with Mermec, sent a Mermec Tunnel Clearance Measuring Systems Brochure (1MB PDF) to share with you.
Nikon Rumors posted a page outlining how Swiss Federal Railways is using an array 5 train-mounted Nikon DSLRs to monitor train tunnel conditions.
This is a very cool use of DSLR technology - regardless of the brand of DSLR being used.