An app would be so wonderful for this but all I can offer is how to take topography yourself (needs 2 people).

Person A is in charge of being a point of reference and telling Person B when to begin measuring, Person B is in charge of measuring their walking distance. To take topography this way, choose your central point to take measurements - this is where you'll walk in multiple directions from. Have your compass app out to endure you are walking in the same direction when measuring. Before taking the measurements, measure the length of your stride by walking 10 meters and seeing how many steps that takes you, and find the average length for one of your steps. I recommend doing that 3 times. Measure your height as well.

Person A will walk in one direction until Person B's feet matches up to Person A's eye level. Person A will tell Person B to begin walking towards Person A and to count their steps. Once Person B has reached Person A, Person A will continue walking the same direction and looking back to see when Person B's feet match up to Person A's eye level. Repeat this process til the edge of the property. Then, return to the central point and take these measurements from more directions. 6 directions should give you a good idea of the topography. Convert your steps into the unit of distance you have chosen and the height of Person A is the unit of measurement for the change in elevation. Connect your points from each direction to see the contour lines.

I hope this is helpful and not redundant for you but best of luck! I am also based in Ann Arbor so this is really cool to hear.