Anyone how much it would cost to build something like the GPS tracker they used?

Alex Weber's custom tracker could be built for maybe $200: http://is.gd/apQ9z You could probably throw in an accelerometer for another $20 to act as trash track's motion detector.

I would think there were cheaper options with less sensitivity using something you could order at sparkfun[1].

[1] http://www.sparkfun.com/commerce/categories.php?c=4

mhm, but those are GPS receivers only. SFE sells the 'ubertracker' for $325 which is GPS + GSM. You could also whack together a super-cheap prepaid phone ala http://instamapper.com