Use TouchID to secure my phone

Here’s a feature I’d like to have on my iPhone (perhaps an app could accomplish this). I have my TouchID set up to work with each of my thumbs. I think I can do up to five login’s. I’d also like to configure it so that if I used one specific finger (pointing finger, right hand, for example) it would lock my phone until I logged in to my iTunes account (or someplace) and entered a password.

So when the cops insist I unlock my phone, I just use my “special” finger and boom, no access. Even if cops know of this feature, they won’t know which finger I’ve configured.