hospitals are not just run as businesses, but they also need to serve the public. as such, you also have ethical and social concerns. there are a several substantial problems with your idea:
-promotes inequality of care based on money. this will likely turn out to be a huge legal issue.
-the decision of something being life threatening should not be determined by patients, but by health professionals.
-substantial change to hospital behavior. the act of creating and incorporating reservations to the ER system will likely be a shock that hospital administrators will not appreciate. (just look at how long it took for doctors to move from beepers to PDA's and cell phones, and also look at the adoption of electronic medical records which is still less than 18% of all doctors) making hospital staff jump through new hoops will increase the resistance of using your technology.
please do not take these comments the wrong way. your idea could work, if you tweaked the business model around hospital constraints, and nothing specific is popping up right now. perhaps other areas where waiting in line is a pain that people will pay for?
How fast you see a doctor in to an ER is not about being on a wait list. It's about how sick you are. If you're close to dying you get in right away. If you're not, we see you as soon as possible. Even then, it's not first-come first serve. And, if you're not here, you're not on the list, and there are no reservations.
And, I can't tell you how many people think they don't have something life-threatening and end up dead. And, there are many people who think that their illness is life threatening and it's not.
All it takes is for you to place one person on a wait list who ends up dead, and you're having a number of long talks with a law-firm. I'm not trying to be a hater, or flame you. I'm the last one to discourage an entrepreneur, but I'm really concerned someone will end up dead, and you'll have a big mess on your hands.
Please, rethink your business idea.