One second is a very frequent update interval that will cause a lot of unnecessary IPC, since the developer's geolocation won't change nearly as often (if at all).

And it seems to me that we don't actually need to query the geolocation on an interval at all. We can instead send a single message to the Firefox process requesting the geolocation, after which the Firefox process can automatically push updates to the Simulator process as they occur until the Simulator process tells it to stop. That seems like a better approach, since then we don't do unnecessary IPC, and updates only travel over the wire as often as they happen.