tlvp actually said:

Sheesh, you don't translate angular measurements into linear ones.
An angle isn't a length. Cheers, -- tlvp

I agree that I'm confused (which is why I am hesitating to respond because
I don't wish to muddy the technical issue further for everyone).

The problem with doing camber at home is different from the problem of
doing toe at home.

For my bimmer, the camber is specified in degrees, and the measurement
tools we're exploring measure in degrees.

We just have to solve the conceptually simple problem of
a. Accuracy to 1 minute of angular measurement
b. Creating a wheel plate that meets that accuracy
c. Measuring to that accuracy with a mobile device

The problem, for my bimmer, is that the manufacturer specifies the toe in
degrees, yet we measure in inches. The conversion confuses me to no end
(which is obvious to all).

However, that specific translation problem may be solved if I trust this
layman's chart, for a similar vehicle:
http://www.bmwdiy.info/alignment/index.html

Which puts the toe-in in inch measurements of:
Front toe (left): Minimum = 1/32", Maximum = 3/32"
Front toe (right): Minimum = 1/32", Maximum = 3/32"
Front toe (total): Minimum = 1/32", Maximum = 3/16"

As with all specs written by laypeople, I can't tell if that toe is to the
centerline of the bimmer or wheel to wheel but since they specify a
single-wheel toe, can I safely presume that the spec is to the *centerline*
of the vehicle?