Send e-mail when a field has a specific value
I don't know when you need to compare the field data,But you can probably do a form alter or modify the Workbench moderation module function.

Then create a component instead of rules and use a parameter if needed for field id or data.In action add send email.

Then you can invoke that component in the function you are using like this:-

rules_invoke_component('rules_save_review_field', 'paramval1', 'paramval2', ....);