Redundancy

No not the personal type of redundancy, but equipment and system redundancy.

Computers - With computers redundancy is sometimes called the N+1 principle.  Have 10 people, then you have 11 computers.  Number 11 is the spare.  Anyone can use it.  Its already been pre-set to use email, the printers etc.
Access to Services - With cloud based services this is pretty easy.  Have another computer that has a web browser.  Or have email delivered to your Smartphone as well as your desktop.
Access to data - With online services you can access your data from multiple devices.  Take local copies of data on your notebook when travelling.  Have a plan with your off site data backups.
Access to the internet - Have normal ADSL broadband backed up with Mobile 3G.  Smartphones have personal hotspot functionality, which provides a small workgroup with internet access.
Access to alternative facilities - If you can't get into your office then where can you go?  Send everyone home?  To a warehouse, to another city?  Can your systems still function if you do this?