For the Web browser, see Sidekick browser
The first popular popup program for DOS PCs, introduced by Borland in 1984. Sidekick included a calculator, notepad, calendar, phone dialer and ASCII table and popularized the concept of a terminate and stay resident (TSR) utility. It was later ported to Windows as a personal information manager (PIM) by Starfish Software, Scotts Valley, CA.
A smartphone offered to T-Mobile subscribers from Danger, Inc., a Microsoft subsidiary. Introduced in 2002 and marketed alternatively as the Hiptop, Sidekick uses the Java-based Hiptop operating system, also called DangerOS. Manufactured by several companies, including Motorola and Sharp, the Sidekick gained prominence in the deaf community early on because the deaf could make unassisted relay operator calls via the built-in AIM instant messaging software.