Sign up + Secure password check
Problem: Some sites tell you your password is not strong enough only after you fill out everything and click submit. Some other sites gives you a huge paragraph of instructions - which doesn't help everyone. For example, if you have a password you always use which is Dribbble858, it almost always pass a security test. When it doesn't, you don't want to read a paragraph to check off each requirement, you only want to know what you need to change.
Solution: An automatically updated requirement list with several seconds of delay after user starts typing in the password field. It starts detecting if the password is strong enough after 2 seconds. If it is, great, you don't see the tooltip. If it's not, it shows up telling the things you need to fix, you can ignore the items with checkmarks.