How can I tell if IPython is running?

I have an IPython notebook. I have a long-running loop that produces no output in one of the code blocks. It's not this, but imagine it was this:

for i in range(100):
    time.sleep(2)

I started the code block running a while ago, and now I can't tell whether it's finished, or whether it's still running.

All the IPython status bar says at the top is Last Checkpoint: 23 minutes ago (autosaved). There's nothing in the browser tab to show whether it's running code, either.

I don't want to start the next block because I don't know if this block has finished.

And I don't want to stop the kernel and add print statements to this block, because if it's 80% of the way through, I don't want to kill it and restart it!

Is there anything in IPython - either the browser window or the console - that indicates what code is running right now?

via Chebli Mohamed