Is this too broad a focus for a business plan?
Jay
No. It is not. You go ahead and write that business plan - start today! If it turns out to be more than 75 pages, then you can carefully edit some of the information out. Make certain that you know a lawyer or a CPA who can help you with some of the details.
Casey Y
I would start different companies depending on the products on offer. POS and process management are perhaps similar enough. Clinical vitals is healthcare related, so that's its own company. Personal security device, that's another separate company. You can start them separately and have them owned by a common parent, or just be the owner of the stock of each of them. Realistically, you will most likely license the technology or sell off the individual companies to larger businesses. Its easier to do this if they are independent on paper.