Pros
I worked as an on call nanny. Some of the pros of the position include: flexible scheduling and the opportunity to work with children. Also, on call nannies are generally paid higher than placement nannies.
Cons
Some of the cons include: not having steady work (As an on call nanny, your work may be heavy or sporadic, other times there is no work at all. There were pay periods where I received nothing), heavy driving distances with little pay (it was not uncommon to drive more than an 1/2 hour (sometimes an hour) to work for a family), and finally inconsistent pay rates (pay rates were different per family and often, the pay rate was not equivalent with the work). Overall, I think this position is great for a college student. I wouldn't however recommend this position for someone that is looking for steady income.