Minecraft Commands – How to Add to NBT Array

You need to specify the radius:

execute @e[name=TestCatch] ~ ~ ~ testfor @e[type=Item,r=5] {Item:{tag:{display:{Name:"Pokeball"}}}}

this will test if there is a Pokeball item within 5 blocks of TestCatch

You could use a setblock command, using a redstone block, instead of teleporting the player right away. The block would be placed next to some redstone, which would trigger a command block to say "teleporting", and run to a line of repeaters to create delay, which is what I assume you want. At the end, have it trigger two command blocks: One to teleport the player, the other to remove the redstone block, to ensure that this would work more than once. Here's a simple schematic:

     C2
C1   ^
R>>>>+>>C3

Where R is where the redstone block would be placed, C1 is the command block that would have the command to tell the player, C2 is the command block that destroys the redstone block, C3 is the command block that actually teleports the player. >> being a right-facing repeater, ^ being an up-facing repeater and + being redstone dust. You could also take advantage of the Scoreboard system so the command block teleports the correct player.