The glute bridge is basically a hip thrust performed with your back on the floor instead of on a bench. By using a resistance band as shown in the video below, the exercise will incorporate more of the muscle fibers involved in gait by requiring the hamstrings to contract at both ends.
This changes the exercise into more of a performance-oriented challenge for intermediate and advanced athletes. It does this by increasing the contribution of the body's deep longitudinal system. This is the line of interdependent muscles from the lower leg to the hip responsible for healthy gait.
This modification and its progressions make for a great activation or warm-up for all deadlift and hinge-patterned movements, as well as antero-posterior patterns with contralateral loads. (That's a bloated way of saying sprints and single-arm dumbbell lunges or step-up variations.) They're also great for helping to ingrain movement skills such as upper and lower body disassociation and multi-planar hip stability.
Here are several ways to make it even tougher:
When performing the exercises, stabilize the foot with a powerful arch by digging the tip of the big toe into the floor. This prepares the lower body for sport and training by exciting the intrinsic foot muscles and calling for greater neural drive into the hip.