has the First Alert SCO501CN-3ST Battery Operated Combination Smoke and Carbon Monoxide Alarm with Voice Location on sale for $33.74 with free shipping over $35 or free shipping with Prime Membership. This is the lowest price it's ever been on Amazon.
- Wireless enabled battery operated combination smoke and carbon monoxide alarm
- Interconnects with other First Alert enabled alarms to create a wireless safety network
- Exclusive voice alarm with up to eleven programmable locations to tell you where potential danger exists
- Photoelectric smoke sensing technology and Electrochemical carbon monoxide sensor
- Includes Test/Silence Button - Low Battery Warning - End of Life Timer and 7-year limited warranty
I personally have one of these in my hallway for about 6 months with no false alerts so far. I really wanted to get the wired Nest Protect but for the price I may just do the rest of my house with these since they have wireless alerts to all the units to let you know which detector was triggered. There are pre-programmed names such as bedroom, master bedroom, downstairs hallway, etc so you can set the location of each unit.