There are a couple of ways to achieve this.
- The first option is to use an Android mobile POS called TabShop.
The basic version is free but not open source. But the Pro version is required for Import/Export of CSV [costs EUR5]. It can work offline.
You can set-up the products by scanning either QR or Barcode, then enter product's name, etc, Cost & price will be set to 0. You can alternatively actually import all the products from a CSV file.
When customer comes along, POS is run as if doing a purchase. You can take the customer's name, address, and email at the checkout by typing it in fields provided. [You can not take picture of business card],
It saves the customer's details and their orders, and can be exported to a CSV file.
It can export the whole data as CSV, which can be loaded by Excel.
Once you get the hang of how to use it, you can enter informaton in a minute or so. You will have to try it yourself to verify.
In the Pro version which costs a few EurosPro version, you can actually sync orders with a googlespreadsheet when the app comes online. I have also used it for syncing with an ecommerce installation - had to write something using its API.
- The other option is to use a Bar Code Scanner. See Previous Answer for an example.