I highly recommend Ubiquiti Unifi video, especially for budget sensitive installs. Check Amazon for pricing but cameras start at $130 /ea for 720p video, IR and built in mic.
Software to turn any PC, Mac or Linux PC into an NVR is FREE (no license fees). Or buy their $350 NVR appliance (runs Linux) and can handle up to 20 cameras. All IP based.
Ubiquiti also has an Android and iOS app to remote view.
http://dl.ubnt.com/datasheets/unifi/UniFI_Video_DS.pdf