One place I worked at, we had the opportunity to bid on a project that would have been used in Antarctica.
The client was looking for a way of tracking people, to see if they were off-site, on-site (but not in the building), or on-site and in the building. They were open to proposals on how they wanted this done.
One solution was to give each person a card, and they would swipe in or out, depending on where they were. The idea was to use the same sort of proximity cards that you'd use to get access to an office building. This is the solution that my boss was initially interested in, as it was similar to some other solutions that we had already written.
Another solution that was proposed was to use Bluetooth. This is when Bluetooth was still pretty new, and no one on our team had used it before.
Then there was my solution: a whiteboard.
In hospitals and other offices where employees are frequently off-site, you'll often see a whiteboard with rows of names, and colored magnets - one per person. When someone comes into the office, they move their magnet into the "in" column. When they leave the office, they move the magnet into the "out" column. My proposal was to buy the outfit a whiteboard, some markers, and a bag of magnets. Then bill the client a princely sum, but still less than what a software based solution would have cost.
My boss wasn't amused.
And the client probably wouldn't have been amused to been billed for a really expensive whiteboard, either.