There are a few options. A $10 Bluetooth OBD2 Scan tool from ebay combined with a phone app works well.
At the moment I'm using an Engine Data Scan Reader from 4Wd Supercentre. I have it mounted on my dash with a generic phone holder (clamp type). It reads everything I need like incoming air temp, battery voltage, coolant temp etc. It can also read and clear fault codes. For the price, I'm loving mine.
https://www.4wdsupacentre.com.au/spe....html?videos=1