Backup GPS tracker – These are usually used for tracking pet dogs, vehicles or cheating spouses. They send location over cellular networks and some use GMRS/FRS. Here is one that lightweight (1.8oz) that uses cellular to email its position to you, includes 1yr of cell service and then its $50 each year after: Garmin GTU 10 GPS Tracking Unit. Just install an app on your smartphone or laptop and you can real time track with ease.
GTU-10 pictured with Sharpie and GoPro for size reference.
If you want something smaller; there is the Tagg GPS pet tracker that is smaller and lighter (1.1oz), but has a monthly fee of $7.99 after 3 months free.
If you fly where there is no cellular service, then you might look into a “direction finding” system. The kind that are used for tracking wild animals.
Note: The Garmin and the Tagg both use GPS with AT&T service as the data link, while other cheaper trackers ‘China specials’ use Euro GSM or US T-Mobile. Choose the one that has the best coverage in your flying area. Do not use A-GPS, its not as good as real GPS.