The other solution that requires no monitoring is a translucent propane tank
http://www.hexagonragasco.com/products/composite-lpg-cylinders We have one from a company that did not follow DOT standards to their satisfaction and who they shut down. it is coming up on hydro re-certification shortly and there were never any failures of the actual tanks so intend to keep it. Having bucked up against government standards in the inspection work I did my skepticism that they just pissed off some some inspector...
The Ragagaso tanks meet specs and are less weight and will not rust and being able to see exactly how much you have and are getting when you fill up.