Actually, if you really need to send entire capability with network package, you may write your capability into CompoundNBT tag and then write this tag into PacketBuffer.
But as poopoodice said, avoid excess synchronization.
The game runs at 20 ticks per second. If your motion is too fast for this, you have to check all the positions your entity moved through in one tick.
Say your motion is 5 blocks/tick then you need to check those 5 blocks, not just the current position.