Compact security alarm for children, bright yellow for high visibility. It's lightweight and compact, with a diameter of 46mm and a weight of 25g, so it won't get in the way when attached to a school bag. It has IPX5 waterproof protection and a battery life of up to 2 years. It also features an 85db loud alarm, which can be used as a replacement for existing security alarms. In addition, it has a function to notify the location information if you register the place and time you want the guardian to check. This allows you to track the activity of people with the dedicated device "otta.b" and respond quickly in case of trouble. In addition, iOS/Android apps compatible with "otta.b" can be downloaded, and there are two apps available: one with both a management screen and a monitoring function, and one with only a monitoring function. 【Note】 I probably bought this when my child was young, but I have never used it. Therefore, please note that I have not been able to confirm whether it actually works in conjunction with the app. Just in case, I will include the URL written on this product. https://qzss.go.jp/usage/userreport/otta_161026.html