Oh sure, on my webserver I just wrote the POSTed image to a temp file, called the command-line utility itself from within my code, and captured the stdout to return back. The command-line utility initializes very quickly so the performance was fine.

The only semi-tricky bits were parsing stderr if anything went wrong (distinguish warnings from actual errors), and the fact that Tesseract doesn't respect the JPEG orientation bit (big problem with iPhone camera images), so checking that and manually rotating the JPEG first if necessary (gibberish otherwise).