Military a/c find them very useful indeed, in fact they're pretty much vital on high performance swept wings. I don't think it is so vital on straight winged a/c.
Useful in the event of a pitot-static/CSI failure though. Instead of having to guess at power settings he can now just fly a circuit on alpha, much easier methinks. I'm not sure how confident I would be in a DIY one as opposed to one designed for that particular a/c.
The various important AOAs are usually discovered by test pilots through hours of well supervised flights. Be careful buddy.