WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
Oh Dear! - Website monitoring, without the hassle
DeskAlerts - Send alerts to any corporate device: PCs, phones, tablets, etc.
Freshworks - Delight your customers, from wherever you are
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.