Does this work for cross-compiled projects as well? Do you only require code that's buildable on the host or also runnable? How would it behave for a firmware codebase?
You can create a program that calculates the histogram of an image or write a sobel filter for an image. Sobel is fairly simple as it's just matrix multiplication.
Get familiar with how to manage memory between the CPU and GPU first and the different types of memories you have available on a GPU