There are some alternatives. I will be specific with the devices I have used and know well. This small, pocket-sized computer can store large amounts of data. It has a small, monochrome backlit screen with a 40-character line. It has the requisite programs to manipulate a calendar, addresses, tasks, notes, calculators and games.
Input is slow and awkward since there is no keyboard.
As a result, I tend to use this computer only as a read device and not for actual data input. Its advantage is that it very easily and quickly synchronizes its data with a conventional computer, either PC or Mac. I actually like the device but think it is still too bulky to carry all the time. If you buy one, I would recommend the Palm III over the PalmPilot Professional for the larger memory and backlighting. This larger and more capable handheld computer has a very readable color screen with a normal 80-character line width.