Airport security devices may well be triggered by your pacemaker and at an airport you should tell the security people that you have a pacemaker so that they do not think that you have a concealed device!
The devices at shops are not usually sensitive to a pacemaker and are unlikely to sound an alarm. It is best not to stand next to them for a long period of time as this may cause de-programming of your pacemaker. (See answer to question 6).