If you want to program the devices, you'll probably want to see (Ab)using currentcost dev boards part 3 for the pinout. You'll also need a PIC programmer, such as the PICKit2. Both the framework and DHT22 (HygroTherm) have hex files, so you don't have to compile the code.
If you do want to compile the code, it was written using MPLABX and compiled with XC8 in free mode.
This contains a basic 'framework' for building your own CurrentCost compatible data device from a CurrentCost Digital Development Board. It does NOT transmit electricity consumption (watts) values - you would need to modify the code for that, as the packet structure is somewhat different.
In its unmodified form, the code will transmit a value of 1 if CH1 sensor pins are shorted, and a value of 0 if they are not. After pairing, this information will turn up in the XML output from the EnviR.
The function getValue() is where the impulse value is set, and this should be the bit of code you want to modify. The impulse value is set as four bytes, making up a 32bit counter. This is called approximately every 26 seconds.
This framework includes pairing code, which is initiated if you hold down the red button for approx 5 seconds. The LED will flash gently on and off when pairing is occurring. This will take approximately 12 seconds, so make sure you have your EnviR ready for pairing before you push it!
This contains a basic DHT22 example, that'll transmit temperature and humidity data in a 'water meter' type packet. You will need to move the pulldown resistor on the digital dev board, and put a suitable pullup resistor in it's place.
Roughly every 80 seconds, the device will poll the sensor and transmit the result in the form of a water meter counter packet. In order to pair with a Current Cost base unit, choose a channel on the base unit, and put it in pairing mode. Next hold down the button on the digital dev board until the LED starts flashing, which is about 5 or 6 seconds. The digital dev board unit will stay in pairing mode for approximately 12 seconds.
Battery life should be pretty good. I have one sensor that has been running for about a year on the same set of AA batteries. However, be aware that the DHT22 really wants more voltage in order to operate well, Once the battery voltage gets down to about 2.8V or so, the DHT22 has issues operating normally. I'd recommend you power it from 3x AA batteries, to give a terminal voltage of about 4.5v. The DHT22 and digital dev boards will be fine, as they are safe to operate up to about 5.5v