I just read an article on edtechreview.in about technology and pedagogy in which they discussed teaching and technology. Do you choose the technology and then write the lesson plan or do you write the lesson plan and choose the technology? Personally, I don't think it is either.
From my perspective of teaching math, it is more important to choose the concept first, decide how you want the concept to be understood by the students and then look at where in the process the technology is best used. Technology is a tool to help students learn the material.
One item taught during transformations is tessellations. I introduced this section by showing pictures of tesselations on my smartboard. I asked questions about what they saw and how they think these were made. We reviewed types of transformations and discussed how they were used to produce certain pictures. This was followed by a video on tessellations and I asked them to design their own tessellation on the geoboard app on the iPad. Once they had their tessellation created, they transferred the design onto graph paper and colored it in. This took about two 55 min periods to complete. The students stayed engaged and we used technology to further the lesson.