Yup Iphone Thats how i did it.. Then took it to 4 Wheel Alignment and to my suprise it was spot on......
I may be interested in one of these as I'm fed up with the mag base on the wing with a plumb line hanging off it - I more often than not end up skelping the mag base off the wing with my head
I use an angle finder (20 off ebay), and a bit of box section with bolts same as every one else. Beauty with the angle finder is you can zero it to the car first so the car doesn`t have to sit on exactly level ground. Someone on here posted up a very similar idea years ago, maybe Deako?.