There are systems that have it built in. My system, which is an Infinite, which I don't think is made anymore, has telecommunication built in. If the alarm goes off, it rings my mobile phone and an automated voice tells me what is happening ie what has been triggered. Although mine uses the landline, there is a plug in module you can buy that you insert a sim card into that use the cellular network instead, in which case it can use either or both. There's no charge associated with either system for the alert beyond your normal call charges. Although I don't think my specific system is till manufactured, there are other alternatives out there.
One thing to realise with alarm systems is they are graded 1-4 (at least in the UK), which represents the level of security they provide from full commercial use to domestic only.
Risk Assessment and Grading of Intruder Alarm Systems | Protecting your Home | SSAIB
Even if the US doesn't use a grading system, it might be possible t look the grade up if sold into the UK.