Are there contraindications with pacemakers?

Pacemakers. Anyone who needs a pacemaker can generally have one. The implantation procedure is quite benign and the devices are generally tolerated very well. The major problem would be if the patient had infection that likely could see the device pocket or its implant site in the heart. We'd hold off till the infection was resolved.
No. Virtually no one is allergic to a pacemaker. There are really no contraindications to pacemaker implantation. Rarely, access to a blood vessel to place the lead into the heart is limited (for example, due to scarring and closure of both subclavian veins).