Wow, you have really wide and important question here! :) So let me answer it step by step. Indeed, various signal jamming devices may be used by different people or groups to block various frequencies, and the hospitals are not an exception. Pacemakers can really interfere with one type of jammers, but both jammer and pacemaker manufacturers are constantly make sure that such situation would be avoided in any way.
The original pacemakers was developed to operate using short-range communication frequency of 175kHz, and there are no civilian jammers that are able to block such low frequency range. Later with the development of medical technologies new pacemaker models have appeared. Now they can use 402-405MHz frequency from the UHF frequency range for longer distance communication.
The only jammer that blocks this spectrum you can see here. As it is clearly seen from its description, this widely available model of UHF/VHF jammer blocks only 140-180MHz and 450-480MHz frequencies, thus its jamming signal is near but not in the interfered frequency range.
Still pacemaker developers are aware of the possible danger and to reassure in the safety of people's lives the have further improved the pacemakers by equipping them with special RF barriers which work as the Faraday cage, protecting the pacemaker inside from the wireless intrusions of the outside world. Thus as a civilian person you can stop worrying about any RF interference between the jammers and your pacemaker, especially if you have the latest model of it.
Every jammer is intended to block the specific frequency range that is declared in its specifications. If those frequencies don't match each other then there will be no interference between them. For example, GSM900 band of mobile phones uses 890-915MHz and 935-960MHz frequencies for its work, and pacemakers use 402-405MHz, so they have no chances to meet in the wireless space. All frequencies are described in details here and here. Thus the wireless signal that is sent by the dedicated in-home box to the server where doctor can monitor the condition of the pacemaker and its owner is not interfered.
In any way, both medical equipment developers and we as the company producing different signal jammers have people's safety, health and life as our top priority and always doing our best to maintain it. I hope my answers dotted the i's and crossed the t's for you :)