The Machine-To-Machine (M2M) applications of Wireless Sensor Networks (WSNs) and Wireless Body Area Networks (WBANs) are set to offer many new capabilities in the EPSRC themes of 'Healthcare technologies', 'Living with environmental change' and 'Global uncertainties', granting significant societal and economic benefits. These networks comprise a number of geographically-separated sensor nodes, which collect information from their environment and exchange it using wireless transmissions. However, these networks cannot as yet be employed in demanding applications, because current sensor nodes cannot remain powered for a sufficient length of time without employing batteries that are prohibitively large, heavy or expensive. In this work, we aim to achieve an order-of-magnitude extension to the battery charge-time of WSNs and WBANs by facilitating a significant reduction in the main cause of their energy consumption, namely the energy used to transmit information between the sensor nodes. A reduction in the sensor nodes' transmission energy is normally prevented, because this results in corrupted transmitted information owing to noise or interference. However, we will maintain reliable communication when using a low transmit energy by specifically designing channel code implementations that can be employed in the sensor nodes to correct these transmission errors. Although existing channel code implementations can achieve this objective, they themselves may have a high energy consumption, which can erode the transmission energy reduction they afford. Therefore, in this work we will aim for achieving a beneficial step change in the energy consumption of channel code implementations so that their advantages are maintained when employed in energy-constrained wireless communication systems, such as the M2M applications of WSNs and WBANs. We shall achieve this by facilitating a significant reduction in the supply voltage that is used to power the channel code implementations. A reduction in the supply voltage is normally prevented, because this reduces the speed of the implementation and causes the processed information to become corrupted, when its operations can no longer be performed within the allotted time. However, we will maintain reliable operation when using a low supply voltage, by specifically designing the proposed channel code implementations to use their inherent error correction ability to correct not only transmission errors, but also these timing errors. To the best of our knowledge, this novel approach has never been attempted before, despite its significant benefits. Furthermore, we will develop methodologies to allow the designers of WSNs and WBANs to estimate the energy consumption of the proposed channel code implementations, without having to fabricate them. This will allow other researchers to promptly optimise the design of the proposed channel code implementations to suit their energy-constrained wireless communication systems, such as WSNs and WBANs. Using this approach, we will demonstrate how the channel coding algorithm and implementation can be holistically designed, in order to find the most desirable trade-off between complexity and performance.