The Twinkly PRO Splitter allow you to connect up to two strings to the 400 series Wi-Fi Controller. Note that this controller can control up to 500 RGB or AWW LEDs in total, or up to 400 RGB+W LEDs in total, so please plan accordingly (i.e. - you cannot connect 2 x 250L RGB+W strings per 400 series Wi-Fi Controller due to it's limit of 400 RGB+W LEDs. However, you may connect up to 2 x 200L RGB+W strings, or 2 x 250L AWW strings).
Currently, the Twinkly PRO app is only available for iOS devices.