"Siren that integrates well with IFTTT (Arlo)"
Buy a bunch and put them all over your house! This siren isn't weatherproof, but you can put it next to an open window (on the 2nd floor) and have it pointed at the street. You can also use it as a door chime so that you know when somebody is opening one of your doors.
IFTTT Integration - This siren works wonders with Arlo cameras. You can set a recipe so that the sirens go off when your Arlo cameras detect motion!
If you accidentally set off the alarm, I recommend buying several remote tags and hiding them around the house. You can also use the remotes as a quick "panic button" for a greater sense of security in your home.
Below is a video of me setting off the alarm on accident. It responds fairly quickly depending on your internet connection.
[[ASIN:B00NFAQV14 Remote Tag RC3R Control System]]