I have written a program that allows task switching on Sony PRS-T1. Actually, the task switching is done by
MoreRecent, which this utility is meant to be used with.
MoreRecent binds to the long SEARCH press. T1 does not have the SEARCH key, but this utility synthesizes a long SEARCH press when the MENU key is pressed while the HOME key is being held. The utility is called Intrans for Input Translator and requires superuser permissions, since it employs Linux input system grabbing and event injection. The utility would probably work with any other application that binds the long SEARCH.
The binary
The source
Absolutely no warranty. The program is public domain.