We introduce VIREO, a web-based software tool for graphical authoring of vibrotactile feedback for mobile and wearable applications. VIREO enables flexible specification of vibrotactile patterns with model-based and free-draw sketch input, and is compatible with mobile and wearable devices that support JavaScript, either natively at the platform level or in a web browser. We demonstrate the practical utility of VIREO by presenting several applications implemented for a smartphone, smartwatch, smart armband, and a pair of smartglasses that integrate vibrotactile feedback patterns authored with VIREO. Also, we present the results of an usability evaluation study involving sixteen participants represented by coders with various programming experience and levels of programming language proficiency, including JavaScript. We discuss our contribution in the context of the results of a Systematic Literature Review that we conducted on the topic of software tools, editors, and platforms developed in the scientific community for authoring vibrotactile feedback. Since one major finding of our review is the little availability of such contributions, we release VIREO as a free web resource for researchers and practitioners that wish to author and integrate vibrotactile feedback in mobile and wearable applications.