Whether it's enforceable or not is irrelevant; what matters is whether or not you can prove that the IP was completely developed on your own time if the company does decide to sue (and whether or not you can afford to prove it). Make sure you keep a time log of when you worked on personal projects, do frequent checkins to GitHub or a similar service (even if you're not working on code), and make sure you don't use company resources in any way to work on it (especially a company computer, even if you're just doing a Google search).
