Animal toxins are renowned for their ability to regulate ion channel activity and hence cell function. Therefore, they have been investigated as lead compounds for the development of analogues with toxic activity or conversely with therapeutic potential. Besides the pharmacological usefulness of animal toxins, there is a second emerging field in which toxins may soon reveal all their potential. The advent of modern biology witnesses the development of novel biotechnological applications of interest for which toxins present tremendous advantages. In this review, we will illustrate how toxins can be derived to carry on novel functions that make them become tools of choice for diagnostic, imaging and therapeutic applications. Among the examples developed, the case of maurocalcine will be detailed. This toxin, discovered for its activity on the ryanodine receptor, a calcium channel, is now entering a new phase of development for in vivo drug or imaging agent cell delivery.