The sensor forms an image and OpenCV detects the actual touch configuration. It appears you can use the raw data from the Arduino, too, but it might be a little harder.

EarthMake Shakes Internet of Things Market with an Arduino Compatible 3.5” Color Touchscreen Controller for $89 ...

This time around, we're seeing the release of a 5-inch variant of the Raspberry Pi Touch Display 2. And if you're on the hunt ...