I'd leave it in the drop ceiling at a strip joint near one of your accounts.
Phone it in as lost from a payphone.
Then everyone will know they are tracking you when "they" find it so easily.
I used to work service and skipped many a lunch working on stuff so when I took 5 minutes for a bank run on friday to cash my check I didn't think it was a big deal.
Same with stopping at a store/mall at 2-3pm for a half hour when I missed my noon lunch to make sure something was done right and completed.
Never had a phone however, I planned my own day including early and late hours as needed for each account, some required 6am service calls some at 8pm.
If they gave me a phone let alone a tracking one I would have quit. I certainly wouldn't talk and drive with one. They are a serious distraction to an organized worker.
Especially with the caliber of calls that would be received, like where did you leave some paperwork, how do you fix this, when did you ship this part, all stuff that could easily wait until the next day or you got back to the office.
But it's their company so you just have to figure out clever ways to exploit the current set of rules they impose, assuming a larger corporation, I was lucky and worked for a smaller one where I was trusted a bit more.
Just my .02, time to get creative.