To do this your best bet is to talk to large numbers of biomedical engineering alumni. As a data point, you mentioned before that SFU has one of the most respectable biomed engineering programs. As another data point, University of Toronto doesn't allow general stream undergraduate engineers to choose certain specialties requiring that extra bit of intellectual horsepower unless you are able to enter (and survive) the more theoretical Engineering Science program. Biomed Engineering is one of the specialties that falls in this category.

I feel the reason that most biomed engineers don't pursue CS-ish careers is because many of them feel that their additional knowledge, training and suffering should be used for more "important" pursuits (grad school, designing life-saving medical devices, etc.). Combined with the general engineering school attitude that their education is more rigorous or harder than probably any other major in university (other than perhaps actuarial), and you have a situation where most engineers freshly graduated (barring Computer Engineers) would view pursuing a CS-ish career as a major step back.

However, given your stated interest in other goals (e.g. cognitive science, human cybernetics/enhancements/augmentation), this may not be a bad path to take provided you are mindful of and can navigate the immediate post-graduation job interviews.

As others suggested in this thread, it seems that you're probably much more geared towards a startup culture, in which case if you've chosen your electives correctly in 3rd and 4th year you would hopefully have had the chance to focus in on data visualization and/or bioinformatics and show an impressive body of work.

If you are motivated enough you may also try to take CS & math courses in the summer, or work on design projects to build up a body of work. Ideally summers would also be taken up with internships also, but at least the studying intensity would be somewhat reduced to allow you to get ahead on other credits/courses/knowledge/portfolio.