Low Budget FPV Airspeed Indicator.
Now that I've "calibrated" it, I'm going to mark the left side of the Z-log.
Red- everything below the window, in danger of stalling.
Green- above that. It'll be increasing in width. I'll have a white hash to mark the upper end of a comfy cruise around the upper window.
This way, I know, at cruise throttle, If i'm above the cruse speed, I probably have the nose down...If I'm below, and this won't be for too long, the nose is up.
Now, with this and the ball compass (which shows you slip/skid, as well) all I need is a turn needle and I have something that approximates a "partial panel" for those full scale instrument guys...