I use a Compaq (now Hewlett Packard) iPAQ handheld with extra Memory Cards and a vehicle cigarette lighter battery re-charging unit.
When birding, I use a software program called "TweetChirp" to listen to bird sounds, broadcast bird sounds, and keep notes, lists and journals that I can upload to my desktop computer when I get home. I can also add more bird sounds into the Directory if I choose to.
The first time I used "TweetChirp" on my iPAQ handheld, I was in a cemetary, bordering Lake Erie, looking for Eastern Bluebirds on a sunny, late February day .. this was in western NY State in the US, so there was still snow on the ground, but I decided to try calling in some Bluebirds anyways.
I played the Eastern Bluebird .wav file sound on full volume and just sat in my car while holding the iPAQ out the open driver's window and towards some trees on the opposite side of a field. I was scanning the trees with my binoculars for a couple of minutes and when I didn't see a thing moving, I put the binoculars down and decided to move to a new location. When I looked out my car windshield, some color caught my eye and when I looked to my right out the car's passenger side window, there sat a male Eastern Bluebird, perched in a very small ornamental tree not more than 4 feet from my car and very determinedly looking inside my car! I have often wondered since.. if the passenger window had been open, would he have flown right inside my car?! VERY effective first tryout of the product!
You can see 'TweetChirp" software for yourselves at...
http://www.tweetchirp.com
I also use my iPAQ Handheld in the field to store digital photographs. I can use as many Memory Cards (which are very small) as I need and just keep uploading the photos from my digital cameras and camcorders onto them, thereby freeing up my cameras' memory card for more photos.
I also use iPAQ to store maps of the areas I am going to and emergency phone numbers and info for the areas. Also my personal phone book and address book.
I also use "QuickClip" hardware (a small IR receiver that clips onto any pad of paper) together with "Ink Notes Manager" software with my iPAQ, which allows me to make notes, sketches, maps, diagrams, etc, in the field, using the QuickClip IR ballpoint pen on any type of paper .. what I put on the paper is automatically sent & saved to my iPAQ handheld .. then when I get home, I can upload it from my iPAQ to my desktop computer.
I have a waterproof, Neoprene, expandable belt case to carry my iPAQ Handheld and Memory Cards .. and it also easily fits in a jacket pocket, cargo pants pocket, or backpack outer pocket. In the rain or snow, I have used it outdoors by sealing it inside a transparent ZipLock sandwich bag with all the air pressed out (or sucked out using a soda straw) and just pressing the buttons and tapping the screen right thru the bag.
A main use of my iPAQ Handheld is to download news, newspapers and magazines using the Avantgo service. In the morning when answering e-Mail and other daily chores at the computer, I download all the various news products I have previously chosen, when customizing Avantgo, to my iPAQ and then at some point in the day when I want a break, I relax with a coffee and read the news. Same deal with e-Books and E-Book Readers I have downloaded to my iPAQ .. I can store as many books as I choose by using additional Memory Cards, as needed.
My iPAQ also runs MS Pocket Excel and MS Pocket Word, should I want a spreadsheet or word processor.
I can also write notes directly onto the iPAQ screen with a stylus and edit & save them. The handwriting recognition that comes with iPAQ is quite good.
There are also GPS units and downloadable maps available as an attachment or built into newer iPAQ handhelds. Although, I don't use these since I use a Garmin Street Pilot III GPS unit.
Birdwatcher