Mobile Phones with more than one Sim card...

At the moment I need to carry two mobile phones around, and it occurred to me that although one phone is considered safe, more than one may not be safe...

For me it is temporary, for others it is a requirement.

The basic solution for me is to have a mobile that can accept two SIM cards simultaneously, or at least one SIM card relating to two different cards from potentially two different network providers.

Does anyone have any important information on the subject? (like existing phones, or safety measures based on more than one phone, etc.)