I'm trying to build simulated instrument time (under the hood) flying an airplane with an autopilot. Let's say I have a safety pilot, I put a flight plan in the autopilot, I put the hood on, I engage the autopilot, and let the autopilot fly the plane for an hour on the flight plan while I monitor the autopilot with the hood on, and I don't touch the controls. Can I log an hour of hood time, and also PIC time? Would I be the sole manipulator of the controls even if I'm not touching the controls? It seems strange, but it seems like I should be able to log the time.
Yes, you can log the time as both PIC and simulated instrument. The Murphy interpretation discusses this:
The FAA considers a pilot's use and management of the autopilot to be the equivalent of manipulating the controls, just as one manages other flight control systems, such as trim or a yaw dampener. The autopilot system's sophistication does not affect a pilot's responsibility to manipulate and manage all control systems, including an autopilot, appropriately. Therefore, a pilot may log PIC flight time as the sole manipulator of the controls for the time in which he or she engages an autopilot.
Note that this means that you must be the one to do any required manipulations to the autopilot. If your safety pilot does them, they become the sole manipulator of the controls. And though you say "I don't touch the controls," you can't really know that beforehand. If the autopilot starts doing something funky or there is a traffic conflict you need to be ready to override it.