After ordering some of JeeLabs JeeNode Mirco Modules and playing with them, I designed my own ones, even smaller. They are compatible with the JeeLabs RF12 Library, also use the ATTiny84 but do not include the JeeNode Expansion header. Instead power and some I/Os are routed to a header.
It also has a coin battery holder included and or some space to add a LDO for powering with other sources. On the lower pictures you can see a DHT11 temp. and humidity sensor connected to the funky.
Eagle files: funky
Sample Arduino Sketch using RF12 and DHT11 Libraries: rfm_test
The code is using some techniques described on the JeeLabs Blog to let the AVR and the RFM module sleep some time in lower power modes. In standby the current is approx. 50uA at 3.3V (measured using multimeter). To measure the current while sending I will need a oscilloscope which I do not have at hand right now.