If you want one get one!! If you plan on having an alarm, you will need a phone! ROOKIE!!
No you don't need one for an alarm. I do not have one. We use our cell phones. The A/C thing is interesting but get your windows tinted and leave your a/c at 90 during the summer and you are allright. Go with Western Alarm they are the best in LHC and the hook it up via radio. It is cheaper. I pay 12 bucks a month for monitoring and it is safer. No phone line for the burglar to cut.
No house phone.....
Cable TV & wireless cable modem.......
Later,
CJG