I have been working for a while as a mystery shopper and app worker and was wondering how you can get into working as an assignment reviewer for such companies as Field Agent, Observa, Gigwalk etc.
I am curious also. I would guess that sending a politely worded email through their "contact us" link would be the way to start. All of the apps have an associated website, and you can find the contact email in the menu at the bottom, usually. Let me know what you find out!