Twipo is used by all of the main Robotics;Notes characters to communicate, and characters from other Science Adventure games such as Takumi, Daru, and Kurisu actively post on Twipo as well.
Within the Science Adventure Series, Twipo largely supplants the earlier FrePara social networking service, which is equivalent to the real-world Mixi. FrePara is mentioned in ChäoS;HEAd and Steins;Gate, and is a service that Sister Centipede used in both titles.
Another in-universe app similar to Twipo is the messaging app RINE, which is equivalent to the real-world LINE. RINE was developed by Daru and is introduced in Steins;Gate 0.