[whamlastxmas]

I make prototypes of stuff like this as a hobby. This is about $15 worth of easily purchased hardware. It'd make more sense to place them in permanent installations around a city - put them on top of traffic lights with a solar panel. People can't reach them and they'll run forever untouched. Have volunteers use an app on their phone that will connect to them via WiFi as they drive past to collect their data. This means not having an expensive (service + hardware both) cell connection needed for the units.

Alternatively, you can attach 433MHz radios to them and place them within about 300 feet of each other so they can all link up and share data and upload through a single unit close enough to a free/open WiFi network.