No instruments? Download one of those in-phone glass cockpits and hold it to your dash.
Please do not do this.
The horizons in the glass-cockpit apps I've seen aren't properly referenced or stabilised, and are little more than novelties. In essence they have the same limitations as your inner ear, and are potentially lethal if used in IMC. (Have a look what happens to them as you go round corners in your car, to see what I mean.)