Here in Los Angeles There is a lot of this happening. Our Ralphs grocery store put monitors in at the cash registers for 6 months (I think was a test). They ended up taking them out. I suspect it didn't work locating them at the register. You wouldn't get out of line to go get an advertised product, and will have forgotten by the next visit! I see them in coffeehouse chains too. Las Vegas is full of this stuff!
What you are describing is called digital signage. I went to a digital signage convention in Las Vegas a few years ago
http://www.digitalsignageexpo.net/. I was shocked at how many people had thought of my idea, LOL! Being a video editor/producer for many years, I was distressed to find out that digital signage was not really video at all, but similar to internet technology. All retail screens are networked to a corporate computer system. This system keeps all the assets (pics, video, text) of a "show". This show is not pre-rendered, but constantly changes. If it's Monday, the Monday specials are shown, if in the morning breakfast items are shown, etc. Lots of assets are timed, and text can be updated in real time and sent to the stores. This is all automated.
Here is a company doing this:
http://www.youtube.com/watch?v=4TwoxzzlhEI&feature=relatedUsing Proshow as digital signage has several disadvantages.
1. Can't show timed assets.
2. Can't easily or automatically update assets from a database.
3. Can't easily divide the screen into several concurrent displays.
4. Does not easily support 9:16 (sideways) display.
Now, you might be able to produce segments to run in an existing automated system, and that appears to be what you are looking into. Your biggest obstacle might be how quick and painless it will be to update.
Here are some tips...
1. Make sure you build your video using their specification: AVI/MOV/MPG, dimensions, codec, bitrate, sound (Y/N). Get it in writing. This will protect you from finger pointing when there is a problem.
2. Clear any logo usage. They will be very anal about color, size, screen time, other unintentional logos in view.
3. If the product offer is limited (Say only on Mondays), This limitation has to be on screen for the entire offer. That way if someone sees it on Tuesday, they know the deal is not valid. This is law in many places.
4. A slideshow for retail is a whole different ballgame than a home presentation. At home you have a captive audience, all you have to do is keep 'em awake and entertained. In retail there is an orgy of distractions, and it's a fight to get eyeballs for a couple of seconds, if at all. It's not entertainment, it's getting a message to the customer. 15 seconds in a retail environment is an hour at home. Expect people to glance at 2-4 seconds of your spot, not watch the whole thing transfixed! Will a random 3 second view get the message across?
5. Demographics - know exactly who they want to target. Selling something to grandma will not work for a pre-teen! Timing, style, content is all different!
I don't mean to come down on your idea at all, it's a good one. You would do well to go to that convention next spring in Las Vegas to see what the market is like. As for ProShow, it's limited as far as you can take it. You might want to look at using Scala
http://www.scala.com/. One thing I found out at the convention was that most of these software packages were for RENT, not sale! That bugged me to no end...lol.
Good luck!
Mark
P.S. another link:
http://www.digitalsignagetoday.com/