Outdoor competetion contestant timing

I have an I-Button based competition contestant timing system but this needs a the button to make contact for it to work. Outdoors this is not ideal. I am now working on using NXP TAG216 for the competitors and something like Keyduino as reader/write in the field. I'm very familiar with ATMEGA devices. Can the KEYDUINO run in very low power mode (20uA or less) i.e. are there any components on the board that take power when the ATMEGA is sleep and the PN532 is sleep. I would power from a 3.6v lithium battery.

Hi, you will have :
- 3.3v (LP2985-XXDBVR33) regulator and the 5v (MC33269ST) if needed, in this case you will have the "on" led too.
- the atmega32U4 at 16Mhz in sleep mode (http://www.home-automation-community.com/arduino-low-power-how-to-run-atmega328p-for-a-year-on-coin-cell-battery/)
- the level converter (http://www.ti.com/lit/ds/symlink/txb0108.pdf) -> 4µA
- the pn532 in sleep mode -> 10µA

Why don't you power up the whole keyduino by the press button?