Here is a no solder/no code solution for knowing your X150's coolant temperature and battery bus voltage;

The OBD Fusion app had a feature that lets you build miniature "dashboards" for your phone or tablet which can be populated with a wide range of gauges, each displaying one of hundreds of OBD PID's as well graphs and a moving map display. The gauges can also be edited after push-holding on their image in the dashboard creation window. The OBD reader I chose is the VEEPEAK OBDCheck BLE+ plus (Amazon $40) and an iPhone 12 mini.

You can get alot fancier, but this definitely does the job, as well as getting you onboard OBD Code reader capability in the car.

 

Nice idea, discussed many times in the forum. Cabrio Bob made a 3D printed module which fits into the ashtray location but has only temp and voltage and some are available for purchase in the Classified section.
There is also a Mr12Volt system that integrates the original TSD with Android Auto (and carplay) with a bit of tinkering.

 

I use Torque Pro and Track Recorder, displays whatever "gauges" you want, plus you can record your drive displaying those gauges. I would upload a video, but they are MP4

 

I use the OBD Link MX+
Don't leave home without it.
I think the cost was $100.
Worth every penny.
Tons of data and gauge styles.
I display it on my phone clip attached to the center left AC vent, eye level.
Rick

Default gauges on my OBDLinkMX+, Coolant temp is great to see!

 

I used the idea and method from @Sean W to install this maybe six years ago. I use it on every drive over a few minutes:

 

And mine, after installing oil pressure and temp sensors back in July, on my HKS Camp2 (definitely not the least expensive way to get gauges).