PDAs have faded in popularity given the presence of smartphones, which are PDAs with phones built in. Most of the features you desire are standard across most such devices nowadays, so there is no shortage of options.

The key is to find the programs to expand your phone's capabilities rather than looking for the exact configuration out of the box. For instance, Windows Mobile users can install gAlarm to add custom alarms, quiz/maze verification (to ensure you're really awake), etc. Likewise with gProfile, which automatically chages your finger, runs/closes programs, etc. based on time/day, scheduled appointments, and cell tower being used.

The best way to pick a smartphone is to try the demo models at local electronics and phone retailers, seeing which you like best. However, I will note that Android is an operating system while Palm and LG are companies that manufacture smartphone. LG makes a large variety of models while Palm was recently acquired by HP after financial difficulties.

Regarding operating systems, iOS is only used by Apple and, while easy to use with thousands of apps to choose from, it is not very customizable. Android is fully customizable, but is still a little rough around the edges. WebOS is only used by Palm and is in a state of transition. Windows Mobile is being replaced by Windows Phone, due out later this year with much anticipation and little history.

Hope this helps,