I don't want a choice, I want health care!

The US is currently having a debate about improving our pathetically incompetent health care 'system'.
The insurance companies who make billions of dollars of profit and don't do a very good job of actually paying for health care (over half of the personal bankruptcies in the US are related to health problems and 75% of these people actually have health insurance) have enlisted (or bribed) politicians to defend their profits under the campaign banner of 'choice'. They imply that a rich selection of insurance plans is a good thing and that a government plan will only offer one choice.
Cynically, when I am healthy I would like to have the choice to not spend any money on health insurance but when I am sick I would like to have the choice to have an insurance plan that offers 'full coverage' for everything that I think I might want to have done whether it was effective or not.
Practically, there should only be one choice that anyone would want for health insurance. This insurance should provide preventive services to keep me healthy and provide care services when I get sick. It's like those cell phone TV commercials when they parodied other companies that made you guess how many minutes you were going to use by asking young kids to make these decisions. Choose too many minutes and you pay too much. Choose too few minutes and you pay too much. The cell company wins both ways and you lose whatever you choose.
I don't want a choice. I want health insurance! Everyone wants health insurance.
This means that the best 'plan' is a single payer (this pools all risks) who is motivated to keep you healthy (not make profits). Sounds like Medicare for the rest of us. This should not be tied to employment so we should not have business provide health insurance. We should have a payroll tax (or other broad, progressive tax) to pay for it.
Unfortunately, doctors, pharma, hospitals, and medical device makers all make more money when they can sell you their products and services and their profit blinds them to ignore the fact that sometimes what they are selling is not safe or effective. We need a government agency deciding which treatments are safe, effective, and necessary.

A Health IT Application Store?

You don't need a 'platform'. An interoperability specification is the platform and it needs to be open to ensure wide adoption and innovation. EHRs now are closed systems with limited data import and export over largely proprietary and/or obscure protocols. This keeps the customer captive but stifles the kind of innovation you are trying to foster.
In order for this to work, you will need to have open interoperability specifications. You need to have a way that an eRx application can talk to the patient index to get patient demographic information and also talk to the EHR to get allergy and current drug information.
Each of these modules needs to be able to generate and respond to messages to send and receive the information it needs. This should all be done through open interoperability specifications.
If you do this, anyone can create a new application that can find the information it needs and adds value.
You can give grants and prizes but I think these should be given for the open interoperability specifications and implementations. Once these are in place, the new applications will arrive.