To meet the Lifetch objectives we formulate the following requirements for ICU:

- the ICU must have a radio interface operating in the license-free ISM band,
- the ICU may have an interface to a public data network through a cellular phone,
- the ICU must be able to perform routing functions between its interfaces,
- the ICU must be able to receive messages at any time,
- the ICU may perform other functions than safety (e.g. map display, audio playback),
- the ICU must not be heavy or in another way interfere with its user's normal activity,
- the ICU must not require the user to recharge its batteries often.