I finally have a Clojurescript application that works basically the way I want it to. It shows a Google Map of the US onto which is added a series of markers. The markers are placed at the positions that I sent a SPOT message on one of my hikes. They are dropped at intervals that correspond to the intervals between me sending them out. The whole thing takes a minute to watch. There are a couple of parts where it seems like nothing is happening – those are winter when I wasn't hiking and a period of time between when the SPOT stopped working and when I got the replacement. The app is here. The source code is on my github page, but it is mostly unedifying.