I've carried ACR Epirbs on Qantas and LAN with no probs..
From the qantas site...
EPIRBs and Personal Locator Beacons
Airline Approval Required - No
Carry-on Baggage - Yes
Checked Baggage - Yes
No Operator (airline) approval is required for the following:
lithium ion
batteries under 101Wh;
lithium metal
batteries with a lithium metal content less than 2g; or
non-spillable batteries under 12V and 101Wh.
NOTE: Watt hours (Wh) are determined by multiplying the voltage (V) by the amp hours (Ah). ie. V x Ah = Wh