The key here is it has to be an ELT. Those others are PLBs and or tracker/messengers.
Some ELTs have the capability of being carried on your person and/or mounted in an aircraft.
Here's a short video. https://www.youtube.com/watch?v=PE4X2PcVhes
PS they are quite expensive. http://www.survivalproductsinc.com/T..._EBC406AP.html
From $998.00 to $2128.00
http://www.pilotshop.com/catalog/avp...36XBoCR0zw_wcB