I know this is old, and asked for a "linux" command in the title, but python is perfect for this and comes with most linux distributions. It's as easy as this:
python -c 'f=open("myfile.txt","rb");f.seek(100);print(f.read(100));f.close()' | SomeOtherProgram
f.seek(n,0) goes n bytes from the start of the program, and f.read(n) reads the number of bytes you want.
I've not found any other options that make it that easy.