There is a lot of talk lately of merging cell phones and PDAs (Palms, portable computers). This is sensible in that you can select an address from your PDA and just call it, rather than carry two devices around. But you're still carrying at least one extra device, that you can drop, break, lose, get wet, etc. My idea is to merge cell phones and PDAs with something we carry with us anyway -- the wallet. If you open a trifold wallet, you can see that it is an ideal screen space for a...