I have just finished the first stable release of my library for portable GPGPU on mobile and embedded systems. Because it uses OpenGL ES 2.0 for GPU-powered processing, it is called ogles_gpgpu. Until now, it supports iOS and Android systems, so embedded systems such as the Raspberry Pi have not yet been tested with it, but this is something I plan for the future.
It is available on github.com and some more information can be found on the dedicated page for this project.