Arduino Touchscreen LCD
- Arduino touchscreens appear to exist in the 320x480 range
- $20 - 3.2" - Ebay - 
- $85 - Sparkfun 3.2" - 
- $20 - 1.8" Adafruit - 
I did a very similar project for home automation in college; unfortunately I don't have the files/code anymore. I used Arduino, several sensors and actuators, and the touchscreen display. Here's some information about the display:
The company 4D Systems offers a wide range of Arduino compatible touchscreens up to 7" - . The displays can talk to Arduino using different communication protocols, such as Serial, I2C, and SPI. Some fairly simple examples along with code and step-by-step instructions can be found in their website - . A specific example is this very simple "Hello World" application - . An advantage is good documentation and excellent customer support from 4D Systems; but there are also disadvantages:
- Proprietary software (but still "gratis") is needed to program the display. The software is not available for Linux.
- Displays are relatively expensive (capacitive touch, ultra bright display with bezel full kits are $99 - $200).
- Some known issues with the micro SD card holding the image files in some of their products; the files can get damaged after ~50,000 read cycles, so there's a need to format and re-write the files every now and then. They supposedly improved this by using "Industrial Grade" micro SD cards. I noticed an improvement, but it didn't fix the issue for good.
I recently used this combination (Arduino + 4D Systems display) for an industrial automation project as well; if I find the files/code this week, I can upload to Github and post the link as an example that goes beyond what you would find in the links I posted.
3.2" LCD library for Arduino - 
We have recently built the Seed Eco-Home - see our Kickstarter from last year: https://www.kickstarter.com/projects/622508883/open-building-institute-eco-building-toolkit
We are implementing a monitoring system for its off-grid utilities. We would like to implement an Arduino-based monitor that shows water, power, and bio-digester gas levels.
Would you be interested in helping us as a subject matter expert - in developing this Arduino-based monitoring system?
Thanks, Marcin Open Source Ecology