IPhone app for invoicing, spreadsheet, etc

We are a towing company, looking to automate and digitalized our business. I'm looking for a method where my tow truck drivers can be on the scene of a job, and begin a tow estimate for the job... A simple form. Once they submit it, I'd like the information to be posted in a spreadsheet (google docs?) and I'd also like a unique number (confirmation or invoice number) to be generated and sent right back to that driver. This would be a great starting point In automating our very busy business and if sucsessful created, would lead to more tasks that relate to this task. These further tasks would be generating documents from spreadsheet data, printing from a mobile device on the fly, etc.