[0xEFF]

  echo ls | bash

[yjftsjthsd-h]

It even seems to work with named pipes, although in my first test it exited after the first command (I suspect I'm accidentally sending a EOF when I echo the command in).

    mkfifo testpipe1
    <testpipe1 bash  # in separate window
    echo ls > testpipe1

[earenndil]

If you have echo and a pipe, then you're most likely already in a shell, no?