IDK...perhaps a time limit to implement for the patent to be registered?
You can hold a Design Patent for 2 years, after which if you haven't achieved a practical prototype, you lose patent rights.
Maybe something along the lines of a "Provisional Patent Application" (which lasts for 1 year)?
A Book For All Reasons Bernard Cole3 comments Robert Oshana's recent book "Software Engineering for Embedded Systems (Newnes/Elsevier)," written and edited with Mark Kraeling, is a 'book for all reasons.' At almost 1,200 pages, it ...