Owlet smart sock 2

Just went to a yard sale and found an Owlet Smart Sock 2 for 15 dollars, but when I was doing research after buying it looks like it’s not available anymore? I’m just wondering if it’s still safe to use/ why it was discontinued, and if I would be able to hook up to it in general? Anyone that has one or has experience please let me know what you think of them or if you know if it’s still useable, Thanks!