Mobile Phone - add picture

We have an extensive Time & Expense app that I want to be able to add the receipt picture via the mobile device camera per expense record.

Adding the expense is easy, but our current method of adding receipts is an event related table with a collection of receipts that are not oriented per expense (yes, that one fixable problem). Now, I could add the "Add Receipt" button to the expense record, but they still have to photograph the receipt first. I want to do this in one step - click the "add receipt" button, the camera open, take the pic, save to the expense record.

Is there a way to do this while avoiding another expensive add-on like FastField license per user seat?

Thank you,