The Construction Probes mod is intended to be a highly performant and non-cheaty means to automate the delivery of materials to construction sites. The construction probes mod uses the on_pre_build event to determine when and where construction is taking place, and it inspects what a player is building with to determine what to send. When construction is identified, the mod searches for the most suitable construction probe, then pulses out the construction materials. The mod prefers to select a construction probe which is inside of the logistic network which the construction is taking palce. If that is unavailable, it will search for the network with a roboport (or a modded roboport-like thing) positioned closest to the construction site. If there are none available within the [configurable] maximum range, it will search for a construction probe which is simply nearby the construction site (not tied to a logistic network). If no probes are found, the construction will be ignored.
The construction probe uses on_pre_built to monitor construction, and various building and demolition events to keep track of its own probes. It temporarily uses on_tick to pulse out construction signals (and unregisters the event if it has nothing it pulse out). If the construction needs more types of items than the construction probe can signal on any one tick, it will use multiple ticks to send the signal (and even merge signals if there are simultaneous builds. I have not attempted any performance profiling, but I doubt that the mod will have any major performance problems - aside perhaps from the logic needed to handle building from the blueprint library.
Construction probes monitor and emit signals for: blueprint building, copy & paste building, direct building, ghost building, upgrade planner actions, and building destruction (resulting from damage). Additionally, construction probes emit signals from anything other Factorio mods care to provide (See 'remote interface' notes)