(Kudos to this video for the idea
I noticed that our city doesn't have a clock/bell tower type building. After some internet surfing, I found out that you could use the decay of items as a timing mechanism. After a few minutes of tinkering I managed to replicate a similar prototype to the one in the video:
Those powered rails are powered by redstone torches; I found out that if you use the detector rails it will "depower" and leave the cart stuck there (if traveling slowly).
(Close up of the cart launching mechanism)
(View of the dispenser and the pressure plate)
(View of the inverter)
This is how the system works: A item (say cobble) is shot onto the pressure plate when the cart runs over the detector rail. An inverter changes this to make an "off" signal. When the cobble despawns (usually 5 minutes) the inverter inverts the signal and turns the powered rails on. This makes the cart run and power the noteblocks (tuned to a chime). When the cart runs over the detector connected to the dispenser, the whole cycle repeats.
Now you may be thinking - What if the chunks are unloaded and the item doesn't despawn? Well, that is the only drawback of this design.
Redstone also stops working at a distance.
Anyway, critique, discuss and debate.