these products are popular in china,taiwan,and it is very cheap,about 1$ or so.it have a asic chip,which i can not see it is name.but i hear it is made in taiwan.this things make for women,who put their mobile in bags,sometimes can not hear the ringer.the little things are tied in bags,when there is a phone call,it can detect it,and will twinkle the led,and beep.it need no connector with the mobile phone,use a small battary,only a thumb size.but this things can not be 50m far away from your mobile,it can not work so far away.
you can search taiwan elec company for some info.
thx.