I like the design of Eric's phone holder, will this work in the Northern hemisphere? Do the apps still work to align?

Yes, Eric phone holder works in both hemispheres. For polar alignment in the Northern Hemisphere, you will need to locate the South Celestial Pole or Sigma Octantis on your phone. Note that the NOMAD rotating plate points in the opposite direction to the phone, so the reference on the phone is reversed relative to NOMAD's actual orientation.