not tried yet in ios7- was fine in previous iOS (haven't upgraded yet...)

All it does is send and receive HTP commands via the web-server in the same way that the catalyst built-in web-server does... So I don't think it would be a catalyst related issue or work any differently between versions...
Worth testing the webserver functionality from another computer to check...

It sounds more like an RC app issue with ios7 unfortunately - so do keep trying to contact the developers.
(not seen an update since I purchased it either...)

S