I need help figuring this out.

We installed hitappoint for bookings but we also have an invoicing system in our site.  We want to skip the payment options in HitAppoint and instead use the invoicing app.

We don't need total integration, just by being able to display the reservation info would be enough, like date, Time in, out, service and staff.

How can we create either a session or global variable of this info so we can use it in another application?

Any help will be greatly appreciated.