You want an alarm.... (Score 1)

Very simple - an alarm does everything that you have asked for, plus covers breakins, etc. Use Ademco equipment (used in banks, armories, etc). Any self respecting geek can wire it up yourself, or you can hire it out. High and low temp sensors are available, water bugs (detect water on the floor), smoke detectors (nice to know when the fire is smoldering, instead of when the neighbors see the flames coming out the roof...). Add in some motion detectors, glass break sensors, whatever you want. You can get a module that allows you to call the house and arm/disarm, check status, speak the temperature in the house, adjust the thermostat, control X-10 modules, anything you want. If you do it yourself, you should be able to do everything I listed here for around $1000. You can get a panel that supports paging (if by some chance you still have a pager), buy a dialer to have it call you, or best yet, pay $10 - $20/month to have it professionally monitored. If something trips, they will call the phone numbers on your list until they find someone to alert.