Is there a way to firm up the consistency of a fresh fruit pie (like peach or apple) - sometimes it gets too "runny"?
This gadget won't make the pie itself less runny, but it will help keep your pie from running.
Apples have pectin in them, which should naturally help keep them from being runny. In fact, I've seen a blueberry pie recipe from America's Test Kitchen/Cook's Illustrated that used grated apples and instant tapioca in combination as the thickener. The reason it didn't use all tapioca was that too much tapioca can lead to a gummy, over-firm gelatin like consistency.
In almost all the fruit pies I make, the key to perfect texture is somewhere between 2 and 3 tablespoons of instant tapioca. Why tapioca? Unlike flour or cornstarch it does not dull the flavor of the fruit.
In the case of some recipes (blueberry comes to mind), I also cook down some of the fruit to make a syrup for binding the fruit together. I do not do this with peach unless the peaches have been sitting in their juices for a while. I do not do this with apple, raspberry, or strawberry rhubarb either.
So try tapioca, but over 2-3 tablespoons (depending on fruit-type), if you find you are dealing with too much structure, switch to a mix with grated apple or straight up pectin.
When I make an apple pie I slice the apples and stir in a small amount of orange juice to reduce air browning and half the amount of sugar called for by the recipe (the other half is added when the pie is assembled). Then I place the apple mixture in a colander over a bowl. Since sugar is hygroscopic there will be quite a bit of liquid in the bowl after 15 or 20 minutes. I reduce this by half in a small pan over low heat. Then I assemble the pie. This keeps the pie from being too wet and reduces the chances of having a big gap between the filling and the top crust.
This question here: what is the purpose of lemon/acid in fruit maceration for pie baking? is perhaps the answer to this question.
The low tech answer is you macerate the fruit to draw the excess liquid from the fruit so your pie doesn't get runny.