Smart-Bracelet

[Smir]

Hello everyone. Me and a couple of my friends are making a smart-bracelet for our school project. We have already designed the features and now are stuck at production stage. We are lacking knowledge about construction of such a device, so we are asking for help. We cannot decide which material would be suitable for that kind of bracelet, considering that one of the features is measuring blood pressure. We also do not know, how we can make the bracelet to shrink, in order to collect data.
We will be happy to get any kind of help on these issues.