Integrating custom application with OpenCart

Hello,

I am finishing to develop a custom application and would like to know how to integrate it with OpenCart. Basically, my application is a wizard that allow user to customize products (for instances, a mug), by adding clipart, text, etc. The last step of the wizard is a big button labeled "checkout".

When user clicks this button, I would like that he would be driven to OpenCart and pass it all the parameters, such as:

- Product code
- Price
- etc

Any clue?

Thanks!

I don't know the implications in regards to security, but you possibly could:
- pass the variables through a session variable
- use cookies
- write to the db, and then have opencart read back from the db