I used to run a 10,000 sqft logistics facility (really tiny in that world) and we kept a stock of about 20 pallets. I seem to remember the wooden ones costing $2-$5 used and the plastic ones less than $50 new. The most expensive pallets I could find from U-Line are $100 or so. http://www.uline.com/BL_8204/Rackable-Pallets
Figure that adding an armored place to put a lo-jack would cost $5-$10 (gotta protect it) and that the actual lo-jack would cost at least $50. It would need to be metal encased with a way to sneak an antenna out, have a "lifetime" battery (lithium-thionyl-chloride, not cheap http://www.all-battery.com/lithiumprimarybatteries.aspx) and the whole thing would have to be molded in to the pallet lest someone get clever and remove them cheaply. The batteries MUST be an integral part of the lo-jack so that someone couldn't just remove the batteries and neuter the device.
Then the data plan to keep it connected up to the world via the internet would cost at least a buck or two every month (in HUGE bulk purchases, individually it's something like $10/mo/device). Worse is that if someone puts them inside a metal building or metal shipping container or metal truck they're going to have a hell of a time getting a GPS fix and/or communicating with the cellular network.
So now that you've done all this your $40 to $100 (max) pallet now costs at least $50 and perhaps even $100 more PLUS it costs you something monthly whether people are renting it or not. What do you get to charge for this? From when I can tell, about $5 per trip. http://www.palletforum.com/tm.asp?m=26458 That's on a nominal $20 pallet cost although they may cost more now, the forum post is 2 years old.
I can't see how building a lo-jack into a pallet is going to be a compelling value proposition given all the limitations.