Cellular telecommunication technology is treated as one of the means to solve the safety problem. Undisputedly, many lives have been saved thanks to the services it provides.

However, we observed three major shortcomings that limit its application in the field of assuring safety. These problems do not occur in the Lifetch system:

- To call for help, the person in danger must be physically able to do it (conscious) and furthermore must be in the GSM or another cellular network system range.

- Localization techniques based on GSM might not work or would provide low precision in sparsely populated areas. Technically, functionalities of the Lifetch system exceed these of enhanced 911 (112 in continental Europe) emergency service.

- An agreement with the GSM network operator is necessary to access location data (if at all possible), which hinders small non-profit organizations.

- On the other hand, satellite systems (like SARSAT) do not provide communication capabilities beyond the basic 'call for help'. Furthermore, the current implementations require the user to manually signal an emergency situation.

The advantage of our project lies also in combining location, multi-sensor and group cooperation services in a single device (ICU), which is not possible by means of a standard PDA. Additionally, unlike PDAs available on the market, our units communicate over an independent radio interface and have an open architecture, allowing them to be extended with, for example, additional sensors. Moreover, through multiprocessor architecture of the ICU, we have achieved a power saving effect, providing substantially longer operation time than any PDA. ICUs are interconnected through a distributed ad-hoc network and submit data for system-wide analysis to a monitoring system acquiring information also from maps, weather services and other sources. Those are the unique functionalities realized by our system through a specialized hardware unit:

- Our units communicate with the Command Center regardless of the condition of the unit owner, transmitting the information about his/her state and location.

- To alleviate the consequences of losing GSM coverage we are using distributed message passing. The ICUs form a mobile ad-hoc network (MANET).

- To decide upon signaling the alarm the system uses a rule-based expert system.