software recommendations - Seeking Field Data Collection Tool?

I'm investigating the options available to my employer for the development of a Geological Field Data Collection tool. We would like to develop an Android app that can run disconnected from the internet (we will be operating in some of the remotest places in the world where there are no wireless communications available) and allow teams of field geologists to input their findings into either a surficial or bedrock geological database.

Does anyone have any advice, know of things to stay clear of that could cause problems, know of any software that will help us meet our objective... or any other knowledge to impart that relates to this project.

I will give a summary of what I have come up with so far as well as a bit of background info of the system design that I have envisioned that will work with what we have already.

We have a Windows Mobile ArcPAD application that runs on Getac Mobile PC/GPS and was used previously for the last phase of our project, but being that several years have passed and technology has progressed we want to take advantage of touchscreen capabilities and get away from having to interface with teeny little icons & keyboard with a stylus.

Okay, so here's what I see:

There is a laptop for daily route/traverse planning with a repository of shapefiles to be used as a background/basemap for the system. The team leader opens an application that allows him/her to select an area and draw a "traverse" (linear route for the team to follow) on it and then load this onto a tablet. The leader does this for up to 10 different 2 person teams per day.

The tablets are then distributed to their teams and they head out with the tablets GPS activated and guiding them to the beginning of their traverse. Once they are there they follow the route laid out for them and identify geological features along the way. The features are points lines or polygons and have attributes that are available to be chosen from drop down lists, radio buttons and checkboxes. This will standardize the language used to describe the features identified.

At the end of the day the teams return their tablets, and the data management leader then imports and incorporates the days findings into an intermediary geodatabase that holds the data until the crew returns to civilization. Once they are back the data is loaded into a master Geological spatial database with surficial and bedrock manifolds.

Does anyone know of anything that I should be aware of?

I'm thinking:

Develop a front end program with C# with Xamarin that uses SQLite to store the geological data.

Is there an open source C# shapefile viewer out there that could be incorporated easily?

How hard is it to use the GPS in the tablet to collect data?