Although ResiDEX is shown on the official website as running on an iPhone device, there are no downloads or instructions to install it on that operating system. Their support system is also not offering anything related to installation and troubleshooting. You have to be an activate customer to benefit from Support.
Use the following website to access that support section: http://www.residexsoftware.com/residex-support
You could ask them about platform compatibility and installation guides as well.