For many DIY Dashboards and Gauges are the finishing touch for a motion simulator, and there are many options available to build just what you want. SimTools can support gauges where the plugin has incorporated that in the game data: http://www.xsimulator.net/community/faq/list-of-games-supported-by-gamedash.178/

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Here is @vthinsel's Dash X2 : https://www.xsimulator.net/community/threads/dashx2-another-dashboard-for-gamedash.9981/#post-200026 along with associated STL files: https://www.xsimulator.net/community/threads/dashx2-another-dashboard-for-gamedash.9981/#post-200171

Here is @jjanu's How-to guide: Real car dashboard for racing games: https://www.xsimulator.net/community/threads/how-to-guide-real-car-dashboard-for-racing-games.11967/

Here is @Haraguchi's Dash board Arduino RGB Leds LC (low cost): https://www.xsimulator.net/community/threads/dash-board-arduino-rgb-leds-lc-low-cost.11806/

This is @vthinsel's digital DashX2, with the libraries available for download and the code available on github: https://www.xsimulator.net/community/threads/dashx2-another-dashboard-for-gamedash.9981/

Here is @vthinsel's guide to building a simple arduino dashboard with TM1638: http://www.xsimulator.net/community/threads/another-simple-arduino-dashboard-with-tm1638.7387/

Here @tombo details building Arduino powered DIY gauges: http://www.xsimulator.net/community/threads/diy-switec-dashboard-with-menu.7056/

There is a tutorial from @eaorobbie
TM1638 Multiply page display with GameDash
http://www.xsimulator.net/community/threads/tm1638-multiply-page-display-with-gamedash.5003/

and a tutorial from @Soraz
Arduino and TM1638 for simple DashBoard 2.0.1
http://www.xsimulator.net/community/marketplace/arduino-and-tm1638-for-simple-dashboard.79/

and a tutorial from @RacingMat
12cm 12V 7segments gear indicator with GameDash
http://www.xsimulator.net/community/threads/12cm-12v-7segments-gear-indicator-with-gamedash.5747/

and a tutorial from @Jamesdio
Arduino RevBurner driving a tachometer
http://www.xsimulator.net/community/threads/arduino-revburner-driving-a-tachometer.5906/

a Tool from @Rufusdufus
http://www.xsimulator.net/community/threads/gamedash.4904/#post-47593
http://www.xsimulator.net/community/threads/graphic-dashboard-gauges.4881/
http://www.xsimulator.net/community/threads/sim-racing-dash-display-for-pc.4788/#post-66286

some examples:
from @hyper1966 http://www.xsimulator.net/community/threads/led-display-for-games.5313/#post-54570

WIP (work in progress):
from @Roonster Fan Control in Assetto Corsa With GameDash and Pololu Maestro?

ELM327 emulator for Game Dash from @soraz:
http://www.xsimulator.net/community/marketplace/elm327-emulator-for-game-dash.139/

Capture and display live game play on 2nd screen?
duplicate a screen zone onto another display
http://www.xsimulator.net/community...live-game-play-on-2nd-screen.6204/#post-68883 from @bsft

Graphic Dashboard Gauges
from @RufusDufus
http://www.xsimulator.net/community/threads/graphic-dashboard-gauges.4881/
sources
http://www.xsimulator.net/community/threads/gamedash.4904/#post-47593

Other DIY Gauges and projects

Here is a description and code to use the M1638 Display and Gamedash by @Archie, provided with the assistance of @soraz (the code) and @eaorobbie (pin advice): http://www.xsimulator.net/community/threads/tm1638-and-gamedash.6807/#post-76490

Simple Dash on Arduino+LCD with SimTools

If you would like to use an LCD as a dash then check out @TOPMO3's work and Arduino code: http://www.xsimulator.net/community/threads/simple-dash-on-arduino-lcd-with-simtools-wip.7029/

Got a hankering for real but still want your digital shift light, then have a look at this BMW Cluster hack by @dahfl: http://www.xsimulator.net/community/threads/echtes-bmw-e36-tacho-real-bmw-cluster-3dof.6323/