I think the decision for which software you want to make for your final year project depends on the field you have decided to specialize in, But ultimately what you need is a time when you will go to a secluded place where you can think and then you start to think of a problem you have seen in that field of yours and you really want to solve, i believe it's in you. Try it and let me know the result.
Computer forensics is a growing field, and there is always a need for competent analysts in that field of endeavor. If that is your interest, then I would suggest that you consider an MS in computer forensics as well as a BS in computer science. The CS degree is a good start on the forensics stuff, but there is a great deal of depth to the field that cannot be garnered in an ad-hoc manner. It is a real discipline that requires a rigorous approach to generate valid results from your analyses.
As for a final year project, there are a number of things you can do, such as keyword/keyphrase searches, deleted file analysis and non-destructive recovery of deleted data (requires physical access to the drive media, and may require specialized tools), etc. Remember, that in forensics, you need to preserve UNTOUCHED the original media, otherwise you have polluted the water and your analyses may not be admissible in court. So, first you make a bit image copy of the drive being analyzed, then you search that. The recovery of deleted data requires access to the physical media so you can do a sector-by-sector scan to dig out what has been deleted or overwritten. However, you have to document your processes to assure the court that you have made no changes to the media itself (read-only operations). However, the bit-image you made at the beginning should hold a lot of that, so hopefully you won't need to get into more technical recovery mechanisms. For the purposes of a senior/final year project, I would think that would not be necessary. For a masters or PhD thesis, that may be another thing entirely.
it's your project. And the first step is for you to research what you want to do.
Just asking others to make that decision for you is NOT the way to go forward.
What'll you do next, ask us to write the design document, implement it, document it, and write your thesis for you as well?