Every once in a while our dryer acts up, or we need to dry something that is too large to fit, such as a mattress pad or a sleeping bag and we find ourselves using our clothesline. If the clothes aren't quite dry in the evening, and I make the mistake of leaving them out on the line, the next morning
the sprinklers will go off, resulting in an unintended rinse cycle.
Suppose, though that there was a tension sensor on the clothes line. The presence of laundry on the line could be easily detected, and a wired or wireless signal could tell the sprinkler timer not to run the sprinklers until the clothes are removed from the line.
A further enhancement might be to have the clothesline send an SMS signal if the clothes remained on the line too long...you could even reply to the signal and re-enable the sprinklers (for example if you went away on vacation and left something on the line; you wouldn't want the lawn to die).