SendView - The best way to track your competitors' email marketing.
SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
Owletter - Keep an Eye on Your Competitors' Newsletters
DeskAlerts - Send alerts to any corporate device: PCs, phones, tablets, etc.
Competitors App - Competitors App helps marketers monitor their competitors' marketing moves in one place, with very little time investment.
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.