Employee Notification Tree

Zombie Data provides an Employee Notification Tree product that allows companies to communicate with their employees in the case of a disaster.  We currently allow the admin to record a voicemail message, deliver that to multiple phone numbers per employee and allow the admin to enter an email, deliver that to multiple email addresses per employee and finally, allow the admin to enter a short Text Message and deliver that to phones/devices that can accept SMS text messages (smartphones, Blackberry devices, iPhones, etc.).  Some phones and carriers allow for different length messages to be delivered. 

Questions:

What length TEXT message should we provide?  Please be reasonable.

Are there other methods of delivery that we should be investigating?