So I'm testing this out. I do not know if littleutils is installed on my shared server, but I thought I'd try it, and I assumed that you rplugin would do a check for it and let me know if it wasn't. As I did not get a warning or message from the plugin, I tried to optimize one image (I tried a png and a jpg). it didn't work.
For the png, it says "Unknown type: text/plain"
for the jpg, it says "Bad response from optimizer"
I guess this means that the littleutils is not installed on my shared server? maybe a quick check somehow would be useful, upon activation of the plugin?