A OSD device is something some people prefer as it applies a virtual head up display on the FPV image. The OSD device is hooked between the camera and radio transmitter hijacking the image and applying OSD using data from the flight controller. An OSD usually applies information such as: virtual horizon, altitude, air speed, heading, direction and range to "home". Home as applied for RTL. This OSD goes for $27 at Banggood.
You probably need additional wiring to connect the kit together but these are the basic devices needed for FPV.
Summarizing purcuses:
- $39 - 808 #16 v2 key chain camera
- $56 - FPV radio
- $27 - OSD device
