(The reason for wanting to use a URL instead of a DOI is that some paywalls have stopped publishing the DOI, so if all I start with is a link to a page at a paywall, there's no reliable way I know of to discover the DOI.)
Oops, sorry - I had actually fixed that, but apparently didn't deploy it properly (it's at whereisscihub.now.sh as well now, which makes it somewhat hard to keep track of). It should work properly now.
In particular, this next url redirects to the paywall, whereas I wish it redirected to sci-hub:
https://whereisscihub.herokuapp.com/go/http://ieeexplore.iee...
(The reason for wanting to use a URL instead of a DOI is that some paywalls have stopped publishing the DOI, so if all I start with is a link to a page at a paywall, there's no reliable way I know of to discover the DOI.)