I have a tilt meter... it measures tilt in both directions... side to side and front to back. I find that the ball rolling in a viscous fluid is good, else it would be sliding all around as the tractor jounces around. Go ahead and get the item from HF... see if it works for you. Be well aware that there is no single angle, even for the same tractor, that is safe... all depends on load, where it is carried..front, back, high, low... and ballast the tractor has. I've had a wheel off the ground numerous times... and the angle was low.
Net... try it... you'll learn a lot and not spend much money... and, go slow anyway and be ready to drop your FEL or 3PH load when a wheel comes off the ground.