We use one dropcam pointed at the valuables in the house (the living room with all the monitors and computers etc.) Dropcam offers a lot of sensible features like camera schedules and location sensitive activity alerts that make the experience of buying the $200 device worth it. There's also night vision and a microphone + speaker. Needless to say, everything works seamlessly across devices, and you can buy 7-day cloud storage for an additional $99 a year.