This weekend I messed around further with mapping my movements. This is not really novel these days, but I want to do things by myself, in order to understand them better. And I want to do it with stuff I wrote or set up myself.
What set me off was realizing that MapServer could handle a GML textfile as a layer. That means I can simply keep a GML file current with multiple points. For example, a GPS trace, as reported from my cell phone, and then have all of those points rendered in a map almost real-time.
Next consider that I can have a map file definition that tracks multiple location reporters in that fashion , and have each rendered as a distinct layer. Each reporter's location can be represented with a different symbol (icon) in the generated map visualization. This means nearly real-time tracking of multiple persons and other entities, assuming they choose to broadcast. The delay is negligible, and dependent only upon fine tuning of the apps and scripts involved.