I always recommend feeding your cat canned food so they get proper hydration. But when you have that cat (like mine) who really loves dry food, please don't free feed (unless they have food anxiety issues - and then call me for a behavior consult.) Feed dry food, and/or cat treats in a food puzzle. Not only does it cut down on the amount they eat but it engages their hunting instincts and cuts down on pent-up stress.
This is similar to the SlimCat but more heavy-duty. Replace the open bowl of dry food with this - and if you have trouble getting your cat to "get it", then just call me and I'll tell you a couple tricks.
You can find the Eggserciser on our store here.