You can enable direct one-wire input on the Raspberry Pi itself. Here's some python code that I use in my domestic heating monitoring. It uses an 'OpenPi' which was an early kickstarter project using a 1st generation R Pi compute board, but any Pi has the one-wire libraries available.
Tony

find all the active one-wire sensors

base_dir = '/sys/bus/w1/devices/'
device_files = []
for n in range(0,3):
try:
device_folder = glob.glob(base_dir + '28*')[n]

print device_folder

	device_file =  device_folder + '/w1_slave'
	device_files.append (device_file)		

print device_file

except: 
	print n
	nend = n

print device_files

#data logging of my OpenPi DS18B20 sensor

def read_temp_raw(n):

print n,device_files[n]

f = open(device_files[n], 'r')
lines = f.readlines()
f.close()

print lines

return lines

@openhardware-io
Great design! I first looked at the Power Integration devices some time ago when I was trying to understand why my wireless thermostat receiver had stopped working (o/p cap gone high ESR). The original design from Power Integrations was for a Bluetooth enabled switch, but this is a nice simplification. It's worth looking at the original design notes to understand how this uses 'leakage current' through the load to drive the switch mode power supply. As far as I can see. the TI TPL7407 device driving the relays was not originally designed as a touch switch, but with its CMOS compatible inputs I presume it works OK with the leakage current from the live mains.
Tony

Carrying on with the "Super Cheap" theme, I have successfully used two Poundshop Lithium ion batteries. They have a 5V USB input and output which can only be used one side at a time. However, connect the two batteries in parallel (+ve to +ve, and - ve to - ve), and you get 2 charger/discharge circuits, so you can power the micro USB side from a USB 5V supply, and the other USB 5V o/p to the Pi. The cheaper ones (1pound) will supply 800mA, but they also have higher power ones for a bit more, especially as they are sometimes on offer.
Tony