Returns a json string like {"devices":["microphone", "Logitech Headset"], "productName":"Logitech Headset", "genericName":"Headset"}, except that in practice currrently the generic and product names are the same and not as helpful as the above. Devices is a list of product names (of available recording devices), the productName and genericName refer to the current selection (or will be null, if no current device).