I'm in need of a simple data collaboration system

I am working on a small project, and we want to collaborate contact information between multiple applications (web, android, mailchimp, etc), all while keeping that contact information secure.

A real database on a server would be the best answer is is overkill for this project and not an option financially. Really just something like a shared file online that all the applications can read and write to.

These were the options I came up with.

1. Google Drive/DropBox - Sharing an excel doc between the users seemed like my best option. Biggest problem here is security. I have found encryption options, but that would force each each in having a way to decode the file.

2. A file/page hosted on the web server. Security here seems to be less of an issue with htaccess. However, reading a file on a server without downloading it with Android seems difficult.

I'm guessing my need is not uncommon and I'm sure that there are good systems in place to handle my need.