Acrobat Pro 9 is perfectly capable of checking the resolution with the built in preflighting module. I don't recall if InDesign CS4 shows the effective resolution of the placed image. Your printer/publisher/etc certainly can work with images under 300 dpi. A 250 or 225 dpi image is perfectly usable. It is a preference of 300 dpi that most printers and publishers have. I always asked my clients and my advertisers (commercial print and magazine publishing days) and got it some of the time. As long as the image was at least 225 dpi for CMYK we were fine.
If you need help with the preflighting function of Acrobat 9 Pro please feel free to call and we can discuss it. All the basics of what you need are in Acrobat 9 Pro.
The views expressed here are my own personal views and are not those of my employer.