A method for low-power encoding of continuous physiological signals, the method comprising: receiving a first signal from a sensor at a first time, the first signal corresponding to a first sample value; receiving a second signal from the sensor at a second time, the second signal corresponding to a second sample value; calculating a difference between the second sample value and the first sample value, the difference corresponding to a first delta value; determining that the first delta value corresponds to a first particular delta value of a set of k delta values associated with a k-ary tree, the k-ary tree including a root node with k branches each corresponding to a particular delta value of the set of k delta values, k nodes at a first depth below the root node each having k branches corresponding to a respective particular delta value of the set of k delta values, and k 2 nodes at a second depth below the root node each having k branches corresponding to a respective particular delta value of the set of k delta values, wherein the nodes at each depth are indexed such that each node is associated with an index number indicating that node's lateral position within that depth of the k-ary tree; in response to determining that the first delta value corresponds to the first particular delta value, storing a first depth and a first node index, wherein the first depth and first node index identify a first child node at the end of the branch corresponding to the first particular delta value; receiving a third signal from the sensor at a third time, the third signal corresponding to a third sample value; calculating a difference between the third sample value and the second sample value, the difference corresponding to a second delta value; determining that the second delta value corresponds to a second particular delta value of the set of k delta values; in response to determining that the second delta value corresponds to the second particular delta value, storing a second depth and a second node index, wherein the second depth and second node index identify a second child node at the end of the branch from the first child node corresponding to the second particular delta value; and encoding the sequence of the first delta value and the second delta value using the second depth and the second node index. receiving a first signal from a sensor at a first time, the first signal corresponding to a first sample value; receiving a second signal from the sensor at a second time, the second signal corresponding to a second sample value; calculating a difference between the second sample value and the first sample value, the difference corresponding to a first delta value; determining that the first delta value corresponds to a first particular delta value of a set of k delta values associated with a k-ary tree, the k-ary tree including a root node with k branches each corresponding to a particular delta value of the set of k delta values, k nodes at a first depth below the root node each having k branches corresponding to a respective particular delta value of the set of k delta values, and k 2 nodes at a second depth below the root node each having k branches corresponding to a respective particular delta value of the set of k delta values, wherein the nodes at each depth are indexed such that each node is associated with an index number indicating that node's lateral position within that depth of the k-ary tree; in response to determining that the first delta value corresponds to the first particular delta value, storing a first depth and a first node index, wherein the first depth and first node index identify a first child node at the end of the branch corresponding to the first particular delta value; receiving a third signal from the sensor at a third time, the third signal corresponding to a third sample value; calculating a difference between the third sample value and the second sample value, the difference corresponding to a second delta value; determining that the second delta value corresponds to a second particular delta value of the set of k delta values; in response to determining that the second delta value corresponds to the second particular delta value, storing a second depth and a second node index, wherein the second depth and second node index identify a second child node at the end of the branch from the first child node corresponding to the second particular delta value; and encoding the sequence of the first delta value and the second delta value using the second depth and the second node index.