This is what I found for screen capturing:

There is an adb method that works by running the Java desktop client net.srcz.android.screencast.Main, but there is no way to capture the screen if you’re not near a PC with adb. I got burnt because I needed to capture the window of a broken captive portal, and the browser refreshes the screen when it’s backgrounded and then brought back to focus… which is a bit fucked up of a behavior.

update

I just found this post which mentions some options that my search missed.