Not that I've ever tried it but, wouldn't that work if you drilled it into your sump?
I don't run a chiller and I do occasionally have heat issues in the summer. What I do now is keep the sump level a little low. If My tank gets too hot I'll add a pitcher of cooled RODI water straight into the sump. Believe it or not that is actually good for .5 degree temp change in the main display. So wouldn't adding the little chiller where water has to constantly pass it be good enough to help bring down the temp if the change needed was minimal?
Granted in the sump it wouldn't have a long contact time.
If I come across one of these on the cheap I may just try it.