Well, Dropcam works off a monthly subscription fee, the cheapest of which is $10 a month:
https://www.dropcam.com/cloud-recording
The Tabs use
Bluetooth Low Energy (Bluetooth LE), which basically can run off a button cell for months or years & have a range of about 100 feet within a Dropcam Pro camera, which acts as a central hub for the Tabs. The idea is that they use an accelerometer to detect motion, rather than a traditional reed switch. In theory, the Tabs could be configured to pair to the Bluetooth radio in the Wink App, IF Dropcam allows that functionality. They do have a beta API program available:
https://www.dropcam.com/developers
That would be
ridiculously cool because you could just buy a $30 Tab for all of your doors & windows - bam, done. If not, I'm sure someone else will make a knockoff. As it is, stuff like this is already available for cheap. INSTEON's battery-powered RF-based open/close sensor is only $35:
http://www.smarthome.com/2843-222/INSTEON-Wireless-Open-Close-Sensor/p.aspx
Same idea for wireless motion sensors...with the advent of low-energy radios, stuff like this INSTEON sensor runs for 6 months off a 9-volt battery: (and can send a low-battery warning to the main system to notify you to change it)
http://www.smarthome.com/2842-222/INSTEON-Wireless-Motion-Sensor/p.aspx
I'd rather not have a month payment and I already have & like my Foscam, I just need some sensors!