Creating an even bead with a caulking gun requires a steady hand and very consistent motion. Any variation and you end up with either big blobs or thin strands.
Take a standard caulking gun, and outfit it with an electronic feed mechanism able to control the speed in which the caulk is squeezed out.
Then add a sensor like those in optical mice. The microcontroller can then see the speed at which the gun is moving, and adjust the flow rate accordingly.
The user can select different bead thicknesses for the desired task. More sophisticated models are equipped with a barcode scanner and database to automatically determine the viscosity of the caulk being used, allowing the user to select thicknesses measurable in absolute units.
As long as you stay within a certain range of speeds, you will draw a perfect bead every time.