AngelSounds, which allows easy monitoring of a fetus's heartbeat. This listing is only for the accessories, not the main unit, as it is a medical device. This model can be linked to an app and record the fetal heartbeat. - Brand: AngelSounds - Model Name: SH-FD20 - Function: Heartbeat monitor - Power supply: 2 AA batteries - Size: Approximately 19.5cm x 5.5cm - Weight: Approximately 120g Used about 3 times, but I stopped using it after I started feeling fetal movement. I kept it in its box, so the carrying bag for the device has not been used.