How to switch between multiple BMP180 sensors?
The BMP180 uses the I2C bus and you cannot simply turn off the device, since that can block the I2C bus. Also it has only one, not changeable address. Thus you would need one I2C bus for every BMP180.

So know you have 2 ways to go:


You could use a Software I2C library and define one I2C port for each BMP. That would use 12 digital pins and you need to find a fitting library, that supports multiple instances. Due to the timed nature of the I2C bus, you most likely will only be able to service one bus at a time.
You could buy a multiplexer chip for both signal lines. Then you could switch the SCL and SDA lines to each BMP. For that you need the multiplexer chips, 2 pins for I2C and 3 digital pins for input of the multiplexer chips (assumes an 8-channel multiplexer)