Actually in a fell/mountain situation they assess it based on the circumstances and decide whether or not to respond - typical scenario is 'calls for help heard' (which is usually someone herding sheep) or 'torches seen high on the fell late at night'. (which is usually some of us out for a late run) Someone (which often used to be me) has then to make a decision as to whether the account justifies a MR response. In this situation an automatic distress signal with no other comms is likely to cause some consideration and assessment of the circumstances - is anyone reported missing/overdue, what are the weather conditions, whats the location, before a call out. I understand a device of this nature malfunctioned or was accidentally activated in the 3 peaks yacht race last year or maybe the year before, which resulted in an assessment of the circs and conditions by police/MR but no actual MR response to the hill. I'm not saying these things would be automatically ignored but if lots of false alarms did occur then this would be an increasing likely response, at least until other information tended to confirm or negate the original call.