pg 27 of GURPS Psionics, allows attaching areas to a person or object so it moves with them. Interlopers use this in http://www.sjgames.com/pyramid/sample.html?id=799
This doesn't appear to be possible in 4e, the closest appears to be:
- use Affliction or Innate Attack with Side Effects to give someone that AE effect as an Emanation (advantage is on by default) but this has trouble affecting people with high resistance or HP
- use Homing on Mobile to cause your Area to follow targets at Move 1.
FAQ re spells[]
http://www.sjgames.com/gurps/faq/FAQ3-6.html#ss6.16
An illusion, as with all movable area spells, has a Move of 5 unless specified otherwise. An phantasmal knight in combat would therefore have a Dodge of 5. Its illusionary armor, weapons, and shield (if any) would not add to this for any purpose.