Nokia had touch screen built into symbianOS from the start. All the API’s were there as was the UI handling. The Psion 5 was based on an earlier version of the same code and it was developed in 1995 or there abouts. In 2002/2003 much worked was done producing a touch based UI (I worked on a few of the apps). We had a customisable Home Screen with drag&drop icons. Multitasking with inter app communication.

Sadly, the hardware wasn’t quite up to it and they were silently dropped instead of working on improving.