Residential Door Alarm

I am looking for a basic $100 or less door alarm for my home; something simple like a keypad and sensor with an alarm to scare off intruders. I'd like to stay away from wired. It is basically to add peace of mind for my parents.

Problem is there is way too many selections out there and I am not familiar enough with the systems to know the difference.

I can install cameras no problem but I'm not up to speed with alarms.

For something super basic with almost no installation and really cheap, look at the GE 45117.

For something more advanced, look at bosch systems.