Right now, this isn't available in the API. It has been requested before, though (e.g. here), and it's something we've got on the books for consideration.
You can do this at compile time, using resource qualifiers. Since the store automatically pushes the correct version to the device, the result will be the same.
This goes as follows:
Do this for every type of device that you want to support.
If you read the resource value at runtime, you'll get "fr920xt" on a forerunner 920xt and "undetermined" on a device that you don't support.