I have started using Z-Wave devices in my rental house, and I like it. 

I find that it is a little un-reliable, but not excessively.  The benefits seem to significantly outweigh the detriments. 

I'm using the ZeeS2 from Homeseer after doing a bunch of research.  It is reasonably priced, although the nodes can be pricey. 

I have a minimalist system, but am always finding new things I'd like to add.  I currently have :

Schlage electronic door lock (don't get a Yale.  bad physical security) : I can remotely set and control that door lock, including giving VRBO tenants access codes or providing entry to contractors.  I have lights in the house tied to an "event" such that if it is night time, and the house is dark, and the door lock becomes unlocked from outside, then the lights inside ramp up. 

Front door switch : The front door opening also triggers the controller to send me an email.  I can tell when tenants check in, when housekeeping comes and goes, and can check to make sure that the front door is closed and locked.

Climate control thermostat : I can check / change the temperature in the house, turn on and off a circulating fan, and lock temperatures or set up timers. 

Fireplace thermostat : I have a gas fireplace, and sometimes folks forget to turn it off.  (Last spring somebody left it on and went to bed and the cabin heated up to 85 degrees)  I just ordered another thermostat.  I am going to set it so that a tenant can turn the fireplace on, and then the control system will shut it down an hour later.

Smoke and CO alarm : self explanatory.   if something nasty happens I want to know right away. 

I have not yet installed garage door sensors and openers.  I also am looking at a way to kick on the power vent on my hot water tank.  I may also put in a motion detector or two as well. 

All in all I like the system.  The main control hub was $200, the door lock was $225, light switches are about $50, contact closures are $25, and the thermostat was around $80. 

Sadly, the documentation for the system is almost non-existent.  The learning curve is a bit steep and long.  There is a forum that has a bunch of tribal knowledge, but still.... somebody should write that down 

Oh... and some light switches. 

One of the down sides is that access to the hub via the internet has to go through HomeSeer's server.  And some of the nodes are a little glitchy (for some reason, the thermostat does not correctly report when the temperature is 76 degrees). 

The system is mesh based, so in order to talk to a node that is far from the hub, you sometimes have to insert a node in-between. 

Interesting, to me for home security. Do they have window opening sensors?

Yes, there are multiple options.  Most of the sensors are a bit large and unsightly.  Some of them are capable of being inserted into a frame and sash, but I don't know how well the battery life / change would work.

Mesh networks communicate frequently, and I don't think a mesh node is a good solution for a security point.  However, you can install a more simple technology such as a simple wifi transmitter which only transmits when a switch is open or closed.  The downside is that you would need a security system receiver which talks to your window switches, and then interfaces to the Zwave system. A little more complex. 

This is definitely something that interests me as we just purchased a cabin that we plan on renting out. 
One of my fears is in the winter if the power goes out I want to be notified.  We contacted an alarm company and because we were planning on installing a Fido Home phone line (which is basically a cell phone in a box that your home phone plugs into) they said they were not compatible with it.  I am now considering designing my own system... but it will be a lot of work.  I will definitely look into this as an option, and see if it would actually work with our type of phone line and up in the mountains in Canada.