Just to add to this thread, there appear to be some very inexpensive 'SIM' cards available for 'internet of things' applications.
For example:
https://www.truphone.com/things/plans/
Claims to provide a prepaid card that costs $12, and is good for 500 MB over 60 months. That is sufficient data for real time tracking and certainly cheap enough to attach to a few tools. IMHO it isn't worth paying $5 per month to track a $500 tool which might get stolen. But $2 per year seems totally reasonable for the insurance.
Our flexible pricing is tailored around the unique needs of your devices. Choose from three plans with the features, services, and support that best meet your needs.
www.hologram.io
Claims $0.70 / month per device + $0.08 per MB, 7x the cost of the above card, but still cheap compared to the $5 or $10 per month from many services
I have no experience with these cheap IOT data plans; just some information for further exploration