I've made the wrist gauntlet for my right wrist, which includes the wrist blades and the eject mechanism. Here's a video from YouTube showing how they work:

Here are a few still pictures to show what the parts look like:

Here's a top view showing the track that I took from two dead CD-ROM drives.

This one shows the track and the motor with its gearing.

Here's a little more detail of the blades. These are done in clear Plexiglas, 1/4 inch thick, but I'll be recasting them in resin.

Here's a still picture of the bottom part of the gauntlet with the blades extended.

At the time I made the YouTube video, I didn't have the top part of the gauntlet sculpted. I've now finished the sculpture, and here's what it looks like. Since the pictures from the movie are kind of dark and blurry, and since I didn't want to copy someone else's gauntlet verbatim, I decided to design my own. The general shape is from the movie and from other gauntlets, but I decided to incorporate a few tech-geek features like heat sinks and some surface-mount ICs.

This is the inside view (i.e. the left side while you're holding the gauntlet out).

This is the outside view (i.e. the right side).

Here's the view from the top, although it's a bit blurry. The four square buttons are intended to be decorative; the actual pushbutton actuators will be near the back in those two round divots.

Here's a picture of the front. The arrow in a triangle, while not true Yautja script, is there for irony. By the time you're encountering Predator wrist blades, you already know you're in danger.