The following radios and radio boards are compatible with OpenTX.

Top of the line transmitter with:
Colour outdoor TFT 480x272
8 Switches 6 x 3-position, 1 momentary, 1 x 2-position
3 Pots 1 x 6-position, 2 smooth
2 Sliders 2 rear, 2 front
GPS and 6 axis sensors
Haptic vibration
Wireless trainer

Smaller version of Taranis Plus with:
Smaller LCD 128x64
6 Switches 4 x 3-position, 1 momentary, 1 x 2-position
2 Pots
No Sliders
S.Port Jack
Haptic vibration

Tray version of Taranis Plus with:
Color OLED top mounted display for basic telemetry data
Quality 4 bearing gimbals
Bluetooth support
2 additional sliders
Safe start and safe shutdown power switch
Haptic vibration
Improved audio circuits

New version of Taranis with:
Haptic vibration
Multi colored LCD background light
Improved LCD display
Improved audio circuits

ARM Cortex M3 32-bit 120MHz
212x64 LCD with gray scales
60 models + infinite on SD
9 flight modes
Telemetry
Advanced audio functions (voice files from SD, vario, ...)
SD data logger

ARM Cortex M3 32-bit 36MHz
60 models + infinite on SD
9 flight modes
Telemetry Interface through Futaba trainer jack
Advanced audio functions (voice files from SD, vario, ...)
SD data logger

Smaller version of the AR9X board
Upgrade option for the Flysky TH9X and Turnigy 9X
ARM Cortex M3 32-bit 64MHz
LCD 128x64
6 Switched 4 x 3-position, 1 momentary, 1 x 2-position
2 Pots, 1 with detent, 1 without detent
LCD backlight option
Haptic vibration option

Arduino (or clone) MEGA2560 16MHz
30 models + infinite on SD
6 flight modes
2 rotary encoders (one can be used for navigation)
Telemetry
SD data logger

ATmega128 8-bit 16MHz
30 models
5 flight modes

Also exist as Turnigy 9X
Atmega64
16 models
5 flight modes
A lot of mods supported (audio, voice, telemetry, rotary encoder navigation, ...)

ARM Cortex M3 32-bit 64MHz
LCD 128x64
6 Switched 4 x 3-position, 1 momentary, 1 x 2-position
2 Pots, 1 with detent, 1 without detent
LCD backlight option
Haptic vibration option

ARM Cortex M3 32-bit 36MHz
60 models + infinite on SD
9 flight modes
Rotary encoder navigation
Telemetry
Advanced audio functions (voice files from SD, vario, ...)
SD data logger

ATmega2560 8-bit 16MHz
30 models + infinite on SD
6 flight modes
2 rotary encoders (one can be used for navigation)
Telemetry
SD data logger