I have been think a lot about this, and definitely, what we need will require a new device never seen before.It shouldn't. Like BigTop mentioned that machine is not designed to do at all what you're after. It does one thing and one thing only. It shoots a stream of sparks straight up in the air. Not sideways, Not a shower, not a burst, just a stream directly up from the machine. And it takes a few seconds for it to get going. If you trigger that machine for only half a second you're going to get nothing out of it. That machine is designed to be used during concerts or something like that where they line the stage with a dozen of them and fire them for 30 seconds at the end of the closing number. Also, be aware of the cost on that type of equipment. Even inexpensive versions of that machine are $400-$500 USD per machine, Quality ones that turn on faster and produce more sparks are considerably more.
And still it doesn't get past my original point that it's going to look bad. This is one of the main things a student learns in theater school. An audience will forgive a lot of things if you let them. Hang a door frame in open space and have actors walk through it, the audience will just believe that that door is in a wall and be happy. But the second you put what appears to be a brick wall there it had better act like a brick wall. If it shakes AT ALL, or moves, or the bricks don't quite look right, people will notice and it will be worse than having no wall there at all. That's not to say I never did a show with walls. But there were a lot fewer of them than should realistically be there.
Here's my basic point. No matter what you do, if you try to make this effect happen its going to cost money. If you go with the cold spark machines its going to cost maybe a thousand dollars and not look very good. Now, you could spend much more and have it look better *maybe* or you could spend nothing and focus on the performance and that ABSOLUTELY WILL make it better. You said in your original message that you wanted to make sure it was safe and it looked good. The best way to do both of those, by far, is to not do the sparks.
That will take... Well i bet you well know it, a lot of research, development and money.
I won't probably do the thing in the wedd.
But after a lot of thinking, i ask myself, is it possible such device?, i may try to build a sort of prototype, but not to use it in any kind of event.