First, I would look at what other agencies in your area are using. This will be especially true if your company needs to interface with other agencies especially with the CAD. 2nd, determine the type of service your company will be providing, medical transport vs 911, and make sure your software will support the reporting requirements. 3rd, Make sure whatever charting/PCR software is compatible with state and/or federal reporting criteria such as Medicare.
You need to have a secure system, and rigid policies regarding how the information is transmitted, secured and released, and who may access the records for auditing and QI. I would recommend consulting with legal council to ensure you don't violate HIPPA.