Happily, the popularity of cargo pants for the last few years has coincided nicely with the proliferation of mobile electronic devices. Another critically important factor to consider is battery life. A mobile device is only useful as long as it has power, so you'll want to be sure to check on this. Most retailers include information on both form factor and battery life in their listings. If the retailer doesn't have them, you can check on the manufacturer's site.
Phones have rechargeable batteries, as do many PDAs.
However, it should be noted that these require that you take a charger with you on any long trips. There are some PDAs that take regular batteries, though you can buy rechargeable batteries for them, too, which saves money and minimizes the environmental impact of old battery waste. The last bit of hardware to consider is the display. This one is really, really important if you plan on accessing a lot of text-based data like news, stock quotes, or email. Basic phones only offer a couple lines of text, while some high-end smart phones offer around 10 lines of text, and PDAs offer larger screens with good legibility.