Making a hologram effect with particle emitter

I wouldn't use a particle emitter for the hologram itself. Maybe for an effect at the base. I would create a simple shader, you don't even need a CG program, that overlays a color on your character to make is solid tone, then have another texture, or the alpha from the same texture, that controls the transparency which consists of solid and transparent lines similar to the force field effect used in the Lerpz tutorial. Have your first tex be the color and your second be the alpha. Then have that texture be offset by a script and you can have that flicker effect fairly easily.

Never tried before but I know particle work quite well. Just set up a mesh emitter and apply small particles to it, that's all. Then it all depends on what kind of effect you want: flickering, vibration, etc.