I am taking care of my mom who has Dementia. I need to know how to keep my mom safe from not leaving the house.

I installed an alarm from Smartcaregiver.com It has a central unit that sounds an alarm and I also ordered the pager that I wear on my belt. Each door has its own alarm transmitter and are assigned a number so I know which door to check.
The pager announces "Hello" and the cpu makes more noise.
In addition I installed "Flip Locks" on the doors. These are cheap and easy for me to operate but DW hasn't been able to figure out how to operate them. Check the home store or hardware stores for the.

There are 2 part door alarms that only ring or vibrate at the receiver, which the caregiver keeps with them. They can also play a variety of musical notes instead of a loud buzzer.

We put a security screen on the front door and we added a double sided locking door handle that locks from the outside and inside with a key.  My mom can look outside but can't open the door.  I know some will say "that's illegal or a safety issue" but its more of a safety issue if she got out and we didn't know about it.  Plus we keep a key nearby but hidden.  We also put a lock up high on the back sliding door, you can also put one down on the slider and get it as the same color as the door frame and she might not see it.  Depending on how far along she is in her disease, you might try a black floor mat in front of the door.  Their depth perception is off and to them it will look like a hole and they will stay away.  My friend also hung a poster on the door.  it looked like a book shelf but I'm sure any type of poster would work.  It's a distraction.   There are some good ideas on the ALZ store website.