As with a lot of things, it seems as though APIs are your friend. There is an API that will pull out the enrollment date of a device, you can use that to get all the devices that have enrolled in say the last 24 hours and add a tag to those to get the new profile. If you wanted it to run more frequently, you could set up a scheduled task to run every 15 minutes and tag the devices then. We do something similar with application tagging for new devices.