Not massively exciting this one but cheap, lightweight and very functional. The FULL SPEED FSD - BBV1.0 5V 80dB 10lm Buzzer is a lightweight (1.3g) buzzer and LED combo that solders just to you buzzer output on you flight controller. When activated it will beep loudly and flash a suprisingly bright LED. I cannot recommend one of these enough to act as a lost model beeper bound to one of the auxillary channels on your transmitter and secondly as a low voltage warning if you have no OSD or you fly line of sight. In case you weren't certain, the LED is very useful for locating in the dark. Just sayin'. Grab a few already and wire them up to anything with a buzzer output.
Just a guy reviewing RC Quadcopter stuff