What is the return on investment for patents?

Apart from Brian comment, I think its always worth to go for provisional before going to VC. Provisional application will substantially protect your idea and will provide you sufficient time to discuss the idea for funding. Also it not a costly process and can be executed by inventor himself.

We should be as protective as we can. Who knows your idea can be our next Google...

It depends on how valuable your invention idea may be. You should contact a patent attorney in the country where you wish to seek patent protection and discuss this in much detail with that attorney. Some patents are extremely valuable and a must for a VC but other patents can be worthless. The market you cite, IoT devices for healthcare would seem to have very high potential. Good luck!

I agree with Brian and just want to add that many patent professionals (attorneys, agents, and consultants) offer a free initial consultation. I recommend talking to one with some familiarity in your industry. I also agree with Ashutosh that the best approach is to have a provisional patent application filed prior to taking to investors, especially since Angel Investors rarely sign non-disclosure agreements (at least in the US). However, I strongly recommend hiring a patent professional to assist you with your provisional application. Having worked for clients looking to purchase patents for their portfolio, I have seen tens of thousands of patents that may have been good inventions, yet the patents were worthless due to the way they were written. Other patents were purchased for much more than the original owner spent on development and prosecution.