We've just released a Ruby version of our SDK, the fiscalrail gem, to make it trivial for Rails and non-Rails Ruby developers to integrate FiscalRail into their products.
Like our Python SDK, it features complete API coverage. We've tried to make the API surface as idiomatic as possible: API objects are organized in modules and the library coerces responses into rich Ruby objects such as DateTimes and BigDecimals.
Try it out today by signing up for FiscalRail. All API calls in test accounts are free!