You need central station automation software.
This can get very complex, depending on how far you want to go with it. Top packages will integrate with (and/or provide) VoIP platforms (to automatically record all incoming and outgoing calls), billing management, GPS tracking to live-monitor guard locations and much more.
Prices start around $10K for a basic setup and can easily go over $100K for full packages with some customization, though a trend in recent years has been to go to cloud-hosted solutions where you pay per-seat per-month.
Major players in the US market, in rough order of marketshare/commonality:
There are also a handful of smaller providers as well.
All of these packages should be able to handle pulling up client information, providing operators with an outline of incident response steps, contact info for the account, event routing (based on matching operators to accounts, round-robin, least-busy, etc.), full logging of data and details related to the incident, and reporting packages to provide incident response reports to customers.
You mentioned remote guarding, which often involves video (in my experience), you will want to pay particular attention to how the video is handled in each platform, some will have strong support for native video, others will use an external platform for the video handling.
The most common platform for external video integration is SureView Immix, and if you are going to be doing mostly remote guarding with video and not burglar alarm monitoring you can run Immix stand-alone in the sense that it should be able to handle all your basic central station requirements.