Then there are scarier things. Will they be allergic to this new food? Was that just spit up, or are they sick? What are the endless things that can go wrong, and can I see into the future and keep my baby safe?

I spent a lot of time as a new parent worrying. I can already predict that I'm always going to stay a little worried about my son, but he's almost a year old now and some of my fears around keeping a baby safe have started moving into the rearview mirror. For example, my fear of SIDS has been replaced with what kind of dangers he can get into as he starts walking, for example. But even as he begins toddlerhood, there's one danger that lurks: hot car death, which happens when children are left in hot cars. 

Especially as heat waves get worse, the danger of leaving my child behind in the car only grows. And hot cars aren't just a summertime fear; the National Highway Traffic Safety Administration warns that an outdoor temperature in mid-60s can cause a car's temperature to rise as high as 110 degrees Fahrenheit. According to the National Safety Council, a nonprofit focused on health and safety in the United States, around 38 children die per year in hot cars.

So when I learned about the Doona SensAlert, a Bluetooth device that sits in the car seat and will alert you if it senses your child remains in the car after you walk away, I wanted to try it. Unfortunately, I also learned that you probably shouldn't use it if you don't already have one of Doona's own car seats.

Calling Cushion

The SensAlert is easy to use: turn it on, set it up in the Doona app (which only takes a few steps; the longest part is adding emergency contacts), place it in your car seat, and you're good to go.

The SensAlert has a three-alarm system. If it senses that you've left your child in the car seat, you first get an urgent notification if your phone goes out of range—I estimated it to be around 10 feet. Two minutes after that, you get a phone call, and finally the SensAlert calls and sends SMS alerts to your emergency contacts. At each level, you can disable the alarm. At the first alarm, you use the app to disable it, but when it calls you, you press a button during the call to disable it.

It's designed to only react when your child is placed into the car seat on top of the device, but I found that for the first day or two it it wasn't calibrated yet. It thought my child was always on the car seat and pinged my phone every time I got near my car and then moved away from it. Luckily, I live in an apartment complex so I didn't get too close that often, but if your car is in a garage you might have a very annoying first day or two. But after day two, it started working seamlessly.

Once it was calibrated, I was impressed how well and consistently it worked to alert me, and accurately reacted to my son being in or out of his car seat. It does make beeping noises when your child is placed in the car. While the beeps aren't too loud, they did get my child's attention when I placed him in his car seat.