I have quite a few hanging baskets and other raised up planters (wall
troughs etc).
They tend to dry out fairly quickly in the heat of summer, much more quickly
than the ground dwelling pots and planters.

Last year I placed a circle of plastic (polythene) in the bottom of each
basket to act as a reservoir, this came about an inch up from the bottom,
meaning that the bottom inch of the basket would be 'waterlogged' after each
watering as the water could only drain through the sides of the coconut
matting once this reservoir was full.
I can't say i noticed any detriment to the plants (just bog standard
fuschias, lobelia, african marigolds, verbena and salvia) from having their
roots wet like this and they didn't need watering quite as much. Are there
any pitfalls to doing this again this year? - is an inch enough? - i could
make it 2 inches.
They are positioned in full sun from about 10AM to dusk, which in high
summer is around 9:30 so watering is a daily (nightly) chore