The mobile phone was initially a technology only associated with voice calls – and primarily constrained to usage in cars. Subsequent generations of mobile phones featured voice connectivity, short text messages, and a small set of simple builtin applications, such as a calendar, address book, and games. Billions of users across both the developed and developing world adopted the mobile phone. As technology advanced, feature phones with basic multimedia capabilities emerged. Telecommunications operators created ‘walled gardens’ allowing feature phone owners to access (and pay for) a variety of contents, such as ring tones. In the late 1990s, NTT DoCoMo established, with the iMode phone, an open system for rich mobile websites.