Semi-pro tip: With Android 4.2.2 here, your Android SDK might need updating
Chances are if you're a serious Android developer you keep your Android SDK updated on a regular basis. But there are many of us who need it just for basic command-line work and don't bother with regular updates. Nothing really wrong with that.
But Android 4.2.2 brings about a new security feature in regards to USB debugging. Whereas before all you had to do was plug in your phone and go (and maybe deal with drivers if you're a Windows user), now there's a gatekeeper on the phone side that you have to acknowledge before any connection can be made. That's what you see above. You have to accept the RSA key on your phone or tablet before anything can flow between the device via the ADB (the Android Debug Bridge). That's an added layer of security, and it's a good thing.