I only recently came across this pretty interetsing app :
uMake
reminds of CATIA one that you sketch and then it translates the lines to 3d volumes. uMake though is only an mobile app (tablets) and i started using it in my ipad mini. Hmmmm… i am so intrigued now to get an iPad pro as now having a) sketcbook and b) uMake (+ the pencil) make it more appealing to me and justify to a sense the cost.