I2C and SPI with Arduino

Didn't look deeply into SPI, but, considering they're both supported by the AVR feature set (look at the datasheet on Atmel.com), it ought to be simple. The thing about Arduino is that there are only so many pins available for expansion - so you have to give something up. My question is - WTH do you have to give up analog pins - why not digital? Anyhow, here's a guy who's been through it :

http://www.neufeld.newton.ks.us/electronics/?p=241

Mission Impossible

Alright, I've had it. I need this gadget now. This is no simple MCU hack of course but..

See what you buy and where you prefer to buy it. Have a bar code reader on your fridge and check items in. Have one on your pantry door as well. Get an idea of the frequency at which you buy the stuff (so you don't have to install weight sensors:) On the other hand, you could check stuff out of the fridge as well - to keep track of usage. Anyway, bottom line is, your fridge will inform your gadget that you need item x.

Then, in the course of your weekly movement, you gadget will alert you when you're close to your chosen store. Sometimes, taking the right exit makes all the difference in gaining that extra half hour of life to do with as you please.

This is going to take GPS and a small form factor PC. But it will be done!