Way back in days of old when I used to write QNX apps, we used to use the IPC message sending abilities quite a lot (see here for a quick description).

I had a quick google (as I don't write Linux apps for a living) and came up with the details of the same mechanism in Linux(here).

So I guess that it would be possible for GPSApp (or the backend to it if it ends up being split) creating a message queue with a known key, so it can be found by any app that wanted the info. Each app in turn could also set up its own queue, and and send the details for that to GPSApp when registering in GPSApps queue.

Then whenever GPSApp has some data to send (an update from the receiver), it checks its queue, and adds any new queues to its list, then just cycles through all of the quese it knows about sending them the same data, that way the app writer has the option of only checking the data when it wants, or sitting recv blocked waiting for the latest data.

So, any comments?