Over the past few weeks we’ve looked at a new take on , , and flexible claw pickup tools to make retrieving lost hardware and tools easier. This week’s tool, the OBD-II monitor, can save your car in a moment of disaster.

This recommendation comes our way from my own toolbox. I’ve been using one of these to look at readings from the car’s Onboard Diagnostic port, built into all cars sold in the U.S. since the 1990s, for the past eight years, and I cannot sing its praises strongly enough. The model I have, an UltraGauge, is essential for keeping up on the health of my cars.

These aren’t to be mistaken for a simple scan tool to pull codes. These tools give you live readings from your car’s sensors and computers. Want to know how far off your speedometer really is from actual? Want to know your intake air temperatures? These can do it all in real time.

Mount the monitor somewhere visible, choose which systems you want to monitor and enjoy peace of mind. Models more advanced than my old UltraGauge can also pull readings from the airbag and traction-control systems. Of course, these can still read and clear codes, too.

I bought my UltraGauge in 2013 to track coolant temps in my Smart Fortwo, which was new. Annoyingly, the second-generation Smart Fortwo doesn’t have a coolant temperature gauge.

Normally, I’d say that’s just a minor inconvenience. However, the car’s computer doesn’t illuminate the coolant temperature light until the engine is so hot it’s roughly 10 degrees from warping its head. If you have a catastrophic cooling system failure, the light will tell you only that your car is dead. That’s where a monitor like this can save the day. You can catch a failure before it kills your car.

I also use it to scan for codes that might trigger the Check Engine Light in the various crapboxes I’m trying to buy. It’s as easy as plugging it in, waiting a minute, then nabbing the codes. I don’t buy a vehicle or go on a road trip without it. I love being able to see what my cars are thinking as I’m driving them.

Now, the UltraGauge I have is fantastic. It’s even pretty small, so it’s not intrusive. However, it’s mostly outdated by modern standards.

Nowadays you can get the same experience using a bluetooth dongle and an app. A few members of my Gambler 500 rally team recommend the Torque app paired to a compatible dongle. There is a large variety of these tools out there, and you can certainly find one that fits your needs. But I do enjoy my old-school setup.

The can be had in wired form for $81.32, or $79.95 for the wireless version. is $4.95 on your preferred app store, but you will need to buy a dongle.

The number of OBD monitors and scan tools out there are vast. If you use one, what do you use?

Do you know of a weird or unique but must-have tool you think every wrencher should have? Do you want to see us put a type of tool to the test and see how it performs? Shoot me an email or drop it down in the comments!