Agreed that the Clamptite tool is overkill for fencing duties but it looks to be a generally useful device to have around.
Lots of DIY you tubes showing "the one wot i made" but not much in the way of useful dimensions or proper plans. Some dimensions and clear picture around the middle of the thread linked here :- **LINK**. if you fancy a roll your own.
But I suspect there are some pesky, non obvious, details that make the difference between "Well it works if I'm careful." and "Really good, I could sell these!". Might be issues with wire type. I can see these things seriously over tensioning ordinary wire.
Best sort of cable tie is probably the type with a metal tongue and lightly serrated tail. Grip is by tongue biting ito the tail rather than via plastic teeth. The metal tongue variety can go uber tight, especially if you use the proper pulling plier tool to finish off. Allegedly the metal tongue ones are exterior rated and won't deteriorate under sunlight. Some of the ordinary variety will give up after a couple or three years out in the weather. Not what they are made for.
Clive.