Health Field is a cut item.
It is unknown what time period this was supposed to appear in.
The Health Field was supposed to give health to the player and surrounding players/sidekicks, at an unknown distance. The health given was 10, 25 or 40 health. This was most likely intended for Singleplayer. It is possible that it healed less at a distance and more as you got closer, due to the large fluctuation in health values.
It doesn't have an associated model, but it was most likely deployed from the Health Field Cannister.