If you're the employee, don't sign it. These things are a huge red flag that this is not a place you want to work. If it was, they wouldn't need a "legal" mechanism to try and trap you there with.
If you're the employer, then shame on you. You should try to make your business a place where people WANT to work, not a place where they are forced to. If you have high attrition, then the problem most likely lies with you and not with the employee(s).
Speaking from experience, any place that wants you to sign one of these things is a scum bag outfit. Plain and simple. There...rant over.