Beat me to it! ;-) I continue to use my (three!) HP 200 LXs in different parts of my lab for different reasons. The most 1-2-3 stuff is for analyzing S Parameters and other RF tasks (conversions, ratios, formulas, Smith Charts).

Two AA batteries power it for a least a month; you could recharge NiMH with the built-in charger if you wanted. I use the PCMCIA card slot to hold a battery-backed SRAM, allowing complete backup (via automatic macros) of the entire machine (dead main batteries are not killers, here in the pre-FLASH world).

And, the comm -- you can plug a special cable in to get 115,200 serial port. And you have IrDA --- I wrote the very first IrDA-compatible 'stack' on that machine (and at the time sold compatible discrete IrDA HW, so you could attach to another end, e.g. a PC).

Sorry to highjack a 1-2-3 thread with praise for the HP 200 LX, but that was (is) one HELL of an awesome machine, still in use in my lab to this day.