What are some alternatives?
When comparing hireframes.com Mobile Sketchpad and Viewports, you can also consider the following products
Whimsical Wireframes - Lightning fast wireframing with real-time collaboration.
Figma Map Maker - Figma plugin to generate map, supporting Google Maps, Mapbox
Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Figma Super Tidy - Figma plugin to easily align, rename and reorder your frames
Method Wireframe Kit - Find your method of being incredibly fast in prototyping.
Easometric Figma Plugin - With Easometric it's really easy to create isometric layers.