I say:
(1) You're THAT broke?? ...Yet your daughter has a cell phone to go playing Pokemon Go in a deserted area at 2am??

Just kiddin'!! Yes, it will take money. But for many folks in the past, that's where family and friends came in - including friends from church. Obviously there is risk here, as to JUST WHAT EXTENT do you trust these people? ...On the other hand, if friends and family can't/won't help, then you're not likely to find investors, even with a great idea that seemingly cannot lose. You would more likely have the idea stolen from you first. Sorry, just being realistic here.
(2) I would recommend getting on good terms with a Podiatrist or two....or three or four! Set up a meeting with them, as a group. Have a prototype made, so that they can see it, hold it, feel it, etc. Make a sales pitch. These are professionals - they'll know in an instant whether it would be worth getting into. Make a business proposition with them. Your idea, their financial investment, and a very, VERY secure NDS (Non-Disclosure Statement). Basically, you sue the pants off of anyone that spills the beans about your idea. Keep in mind, you have to have proof, which "can" be all but impossible. ...Just make sure you don't use the word "sue" with the doctors any more than absolutely necessary!! Most medical personnel nowdays are SUPER-scared about potential lawsuits!! Many have insurance against lawsuits, but it's still very expensive. Every possible additional risk is something they
WILL shy away from!! ...Just keep that in mind.
I'm not nearly the best person to be giving such advice, but then it's oftentimes easier to "give" the advice than it is to take "your own" advice. I've had dozens and dozens of great ideas all my life. I know that because dozens and dozens have been marketed. Am I the first to come up with these ideas? Maybe not. Your exact problem stops many folks dead in their tracks. It's all a matter of how much you want this - how far are you willing to go and how hard are you willing to work and how much are you willing to risk to make it reality. I've never liked this saying, but this really is a dog-eat-dog venture!!
Even if you're able to do the testing (with help from the docs), get the funding (with help from the docs), AND get the thing patented and marketed, you can expect that there will instantly be people out there trying to change your design ever so slightly that they can make their own version and get it patented and marketed, albeit at a greatly lower cost, as you will have done virtually all of their work for them.
You've done the easy part - you've had an idea. Have you built your prototype yet? Have you applied it yet? Does it work in real-world conditions? Great - you're now 10% of the way there....maybe not quite that much! And I mention this because, the doctor(s) will most likely be looking at a huge chunk of the investment. Ideas are a dime a dozen. Literally!! Having the means to put ideas into action - THAT'S where the real money is.