This pressure sensor from Freescale is a great low-cost sensing solution for measuring barometric pressure. At 1.5 hPa resolution, it's not as precise as our favorite pressure sensor, the BMP085, which has up to 0.03 hPa resolution so we don't suggest it as a precision altimeter. However, it's great for basic barometric pressure sensing. The sensor is soldered onto a PCB with 10K pull-up resistors on the I2C pins.
This chip is good for use with power and logic voltages ranging from 2.4V to 5.5V so you can use it with your 3V or 5V microcontroller. There's a basic temperature sensor inside but there's no specifications in the datasheet so we're not sure how accurate it is.
This chip looks and sounds a whole lot like the MPL3115A2 but this is the less precise version, best for barometric sensing only