There's three things that I can think of that you can use:
1. Carbon Dioxide powered Whipped Cream Dispenser
2. Milk Frother from a cappucino machine
3. Immersion blender
Making a foam also works best when combining the liquid/sauce with a stabilizing agent such as gelatin soaked in cold water or lecithin.
I've found that the immersion blender works well with thicker liquids like say, if you want to foam a beurre blanc or a thick cream reduction. For thinner liquids, the dispenser works best. But you can use either or, the key is the stabilizing agent. The milk frother would be as a last resort.
"Boldness has genius, power, and magic in it."
Johann Wolfgang Von Goethe