Q.Many apps for Android let you document your bike ride and provide health data, but are there any apps that provide audio navigation for a fixed route that I can listen to through Bluetooth headphones while my phone is stored in my backpack?

A. The free Google Maps app includes an audio navigation function for driving, biking and walking excursions. Once you select your chosen route and start the navigation, the app guides you by audibly announcing each turn along the way. If you happen to miss a turn, Google Maps will reroute you back on track.

While Google Maps is a good general tool for finding your way around (and finding out what is around you), there are other map apps that combine directions and audio navigation with features designed for cyclists. For instance, Locus Map Pro ($7.48 in the Google Play Store) has turn-by-turn navigation, trip recording and a cycling computer. The free OsmAnd Maps & Navigation app advertises similar features.

As with any app under consideration, read the reviews and check the permissions requirements before installing it. Keep in mind that navigational apps that constantly use your phone’s location services feature for mapping and navigating often run down the battery more quickly than usual.

Powering Devices in Emergencies

Q.How do you recharge a smartphone or tablet during a natural disaster or blackout? I have an external battery, but it’s only good for a few charges, and I live in Portland, Ore., where the sun doesn’t always shine for solar power.

A. USB chargers powered by a hand crank, like the K-Tor Pocket Socket and several models from Eton, are an inexpensive solution. If you are outdoors or in a place where you can have a small fire, the BioLite CampStove ($130) burns wood and creates electricity to charge a smartphone.

If you do not want to turn a crank or start a fire to make juice, a small battery that works as a generator is another option. Duracell has a line of Powerpack portables that include USB and electrical jacks; prices start around $140. If you have a car in a well-ventilated area, a USB car charger and enough gas to spare, you can power up your battery that way as well.

TIP OF THE WEEK Although the site has been plagued by some reliability problems, Wikipedia’s more thorough articles include citations from other publications for factual support and can be helpful. The site also includes tools for easily making PDF files of articles to download — or even e-books of collected articles with Wikipedia’s Book Creator tool.

To create a PDF of an article open in your web browser, go to the Print/Export area on the left side of the Wikipedia window and click Download as PDF. The site converts the article into a PDF with two columns of text and any accompanying photos or graphics on each page; footnotes for reference articles are included at the end. You can print the formatted article right there or download it directly for later use.

If you want to collect several articles and turn them all into an e-book to print, download or transfer onto a tablet, click the Create a Book link under Print/Export on the left side of the browser. Once you click the Start Book Creator button, Wikipedia displays a box or link on each article page with the option to add that article to your book. Once you have added the articles, click the Show Book link to edit it or have Wikipedia render the whole collection as a PDF to download, print yourself or order as a preprinted book.