Connect IQ is Garmin’s technomagic that allows third party developers to build plug-ins that run on Garmin’s own devices.
So far it’s only shown up on the various Garmin watches, but DC Rainmaker has posted that from 30 September the newer Edge GPSes (1000 and 520 models, but sadly not my 810) now have beta access to most of Connect IQ. You can’t get custom watch faces (nor would you have any use for them on an Edge…), but you can get apps and custom data fields.
This is particularly cool news for electric bikes, as it gives manufacturers of motors the option to stick their controlling software in an Edge app, rather than having to design and produce a dedicated control unit. As well as keeping your handlebars cleaner (and reducing the number of gadgets you have to remove when you lock up), one would optimistically hope this might result in slightly reduced costs for e-assists if you already have an Edge.
The custom fields would also be handy for any weird and wonderful data collection you might be planning. Perhaps measuring road surface quality through vibration captured on an accelerometer, or the space given to you by overtaking cars using a laser range-finding device (Ian Walker has a guide here, if you’re interested). Or perhaps you really feel the need to have your tyre pressures displayed on screen—here’s the gadget that will sort that. In short, if you can get the data to the Edge through Bluetooth or ANT+, the Edge will display it (and by the end of Q1 2016 it’ll also record it).