The main manufacturer of rowing machines (ergometers) is a company called Concept 2.  The cheapest ergometer one can purchase from them new is $900, these are expensive machines.  This is primarily because of the technology that they use.  These machines apply resistance through a fly wheel that is attached to a fan thus proudcing air pressure.  All of this is shown on a monitor.  Therefore, the price of an erg would be more than halfed if one were to apply the resistance through a different mean.  I decided to just that and apply resistance through elastics.  This way, one would get the same resistance when pulling as they would with a normal erg.  However, there would actually be more of work out the elastics could there would be  more resistance on the way back to the front end of the stroke due to the tension on the elastics.  In addition, Concept 2 ergs take up a lot of space, this collapses into a box that would mount on the wall, and when wants to work out they would unfold the erg out from the wall.  In addition, the only way to know you are rowing with poor technique on a normal rowing machine is if a coach tells you.  This device would be used off of the ground and the user would be kept up by the elastics on the handle, however, the user would still end up hit the ground if they were using poor technique.  Therefore, in order to not hit the ground one has to maintain good technique thus making the device self correcting so anyone can use it.  Therefore this device is deviating from the focus of simulating rowing on the way and putting more of a focus on getting a good workout.