One can make it in 10 minutes and hide any gadget or also that money you don't want to spend ;)
Also good enough for keeping small valuables safe.
Step 1: What You Need?
Step 2: To Begin With..
Advice: It is better to leave extra fabric at the bottom, since smaller fabric means a smaller pocket and high chances of losing valuables. The bigger the fabric, the deeper the pocket!
Next, get your needles and thread ready.
Step 3: Start Sewing
Note: You may or may not sew the top.
Step 4: Good to Go :)
Remember: DO NOT make a secret pocket at the knee because it would provide discomfort while sitting!
Above or below the knee is good enough.
NOTE: I put money in mine, you can make your's for for your phones or an ipod too ;)
Or infact, just for your earphones (which get lost too often).