That App for iOS particularly suits the protocol defined by Particle. If you want to migrate this App for WICED application, then you should implement the protocol in your application as well. It's a little complex and I would not suggest you to do such a lot of work.
I don't know exactly what Apps may work for you, but as long as the App implements the TCP/IP communication, then you can refer to it to send credentials to WICED application and store it to DCT. The protocol for transmitting credentials can be defined by yourself, secured or plain text for example.
Also, you can refer to the config-AP example in WICED SDK to implement an HTTP client on your iOS/Android device to send HTTP request to configure credentials. This is a much easy way to achieve your target and you nedd NOT to do much work on the WICED application side, since many examples in the SDK related to WiFi have implemented this protocol for user to configure credentials.