Dominik_E:
Thank you for your reply Jack.Your project is really interesting and the design seems to be very versatile. I'm sure I will have to take at look at your code at some point.
I read that you had your prototypes made by ITead. How pleased were you with quality andservice? I was thinking of ordering my boards from them as well even though I have no idea of what I will be doing with 20+ pieces... I can't populate them anyway the sensors and the RTC are pretty pricy.
Thanks! iTead does good work, although I have been leaning more towards Seeed Studio lately. The two seem to produce identical boards, their pricing and specs likewise seem the same. Seeed seems to give me a little more consistent turnaround time so that's the only reason I've been preferring them lately. One difference is that Seeed will do five copies of a board where I think the minimum is 10 from iTead. But the prices are reasonable enough that I don't worry much even if I only need one or two boards. Funny thing, when I have extra boards, it's not hard to find uses for some of them 
Back to your pcb - Why did you chose an eeprom as the main storage over an sd card? For power saving reasons or possible card failure if the device is deployed in difficult conditions (I am thinking of possible corrosion of the sd card contacts)? How do you upload the data to your pc after you gathered it?
Power was probably my first consideration, but I think the EEPROM took less space on the board, and also uses fewer MCU pins, effectively zero since it shares the I2C bus with the RTC. SD would have required the SPI bus, plus a slave select line and signal level translation. By using EEPROM, more pins are available for sensors and the SPI bus is unused. Not that an SD card couldn't have been made to co-exist but neither would it have made things simpler.
Logged data is transferred to a PC using an FTDI cable or breakout board, exactly the same as would be used to program an Arduino Pro Mini, Adafruit Boarduino, or any number of other clones.